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  • Computational Chemistry and Molecular Modeling  (696)
  • 1980-1984  (696)
  • 1925-1929
  • 1984  (363)
  • 1980  (333)
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Keywords
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  • 1980-1984  (696)
  • 1925-1929
Year
  • 1
    Electronic Resource
    Electronic Resource
    Masthead (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170101
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  • 2
    Electronic Resource
    Electronic Resource
    Second quantization for composite particles, reactive collisions, and unstable particles (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 25-35 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The salient features of generalized second-quantization representations for nonrelativistic systems of composite particles are reviewed and their application to a reformulation of the quantum theory of reactive collisions is discussed. Such representations allow the properties of the bound composite states to be built explicitly into the algebra of states and observables. A single unperturbed Hamiltonian simultaneously describes the free propagation of the various species of bound composites as well as of their unbound constituents, while the interaction Hamiltonian describes only true scattering and reaction processes. The inclusion of the binding of all composites in the unperturbed Hamiltonian cures the divergences in the Born series arising from bound-state poles. Unstable composites can be included in a natural way, leading to an explicit representation for the kinematics and dynamics of their decay and their contribution to collision phenomena.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170103
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  • 3
    Electronic Resource
    Electronic Resource
    Interventions in the panel discussion on measurement process and interpretation of quantum mechanics (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 83-84 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170108
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  • 4
    Electronic Resource
    Electronic Resource
    Coordinate measurements and operators (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 47-74 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Relativistic quantum-field theory provides the machinery for calculating wave functions or probability amplitudes depending upon space-time coordinates. The currently accepted theory, however, fails to provide position operators and a means of measuring particle coordinates that are consistent with Dirac's properties of physical observables. This is because it calls for a space position probability distribution at a specified time. This paper shows, however, that space-time event coordinate operators, together with a corresponding measurement procedure, can be found that are consistent with Dirac's requirements. This is done through a reinterpretation of the amplitudes computed by field theory and does not involve any change in that mathematical formalism. The measurement of the space-time coordinates of an event is accomplished by detecting the absorption of a photon by a particle from each of two light pulses designed to overlap at a given point at a given time. If a final emitted photon has an energy whose sum with the final particle energy approximately equals the sum of the mean energies of the pulses, then the absorption of the two pulse photons must certainly have taken place within a distance the order of a Compton wavelength of the small space-time region of overlapping pulses. This is clear from the fact that the high energy required to confine the pulses to very small volumes must throw a particle absorbing them far off the mass shell. Thus the absorption of the two photons throws the particle into a narrowly confined spatial wave function that must decay extremely rapidly - to within a Compton wavelength, a delta function in space-time. This delta function is the eigenfunction of space-time coordinate operators Xμ and is the scalar product of vectors in a Hilbert space spanned by spin-space-time kets large enough to contain the operators of the Poincaré group. These event operators transform properly under the action of Poincaré operators but do not commute with the mass. If the Compton wavelength is not negligible compared to the accuracy desired in the coordinate measurements, individual coordinate measurements are no longer possible. Nevertheless, a large number of repeated coordinate measurements can be carried out to produce a coordinate probability distribution. This distribution can be unfolded to find a true coordinate probability distribution if the charge form factor is known from basic theory. An analysis of laboratory particle detection techniques shows that they actually determine space coordinates and energy rather than spatial coordinates at a given time. When this fact is included, the Klein-Nishina formula can be derived using the electromagnetic four-vector potential as the photon probability amplitude wave. To clarify the meaning of the observables, a mass-momentum measurement is described.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560170106
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  • 5
    Electronic Resource
    Electronic Resource
    Fiber bundles, sheaf theory, and generalization of differentiable manifolds in physics (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 85-97 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some aspects of fiber bundles, sheaf theory, and possible generalizations of the notion of differentiable manifolds are discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170109
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  • 6
    Electronic Resource
    Electronic Resource
    Notes on asymptotic series by H0-strictly singular perturbations (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 99-106 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Let two strongly continuous one-parameter semigroups of contraction operators, {Z(t); t≧ 0} and {Z0(t); t ≧ 0}, determine physical evolutions realized in the Hilbert spaces ℋ and ℋ0, respectively. We consider the mappings under Z(t) and Z0(t), when the infinitesimal generators G and G0 belong to a product class, properly defined with respect to an H0-norm. The inversed transform of each side in the identity R(λ, G) = R(λ, -iH0)-iR(λ, -iH0)VR(λ, G), which represents a simple algebraic decomposition of the resolvent of G, converges on Ψ if and only if Ψ ∊ D(G). By iteration an asymptotic series emerges, when t → 0. Numerical considerations of this approximation in its first order may support the form of a deviation from the pure exponential decay when the semigroup is compared with a integral transform corresponding to a certain self-adjoint H0 in ℋ0. The deviation may hardly ever be observed and it is therefore most fruitful to discuss the results inside the framework of the enveloping algebra of the semigroups.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170110
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  • 7
    Electronic Resource
    Electronic Resource
    Irreversibility, decay, and asymptotic dynamics (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 107-120 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper contains the skeleton of one lecture, and of two raporteur's interventions, made at the Sanibel Symposium in February-March, 1979. The task asked of this lecturer was to present an outline of the program of nonequilibrium statistical mechanics, and to indicate some of the recent developments in our understanding of this program. Section I lists a few of the principal physical ingredients of the theory. The possible implementation of certain aspects of the program is demonstrated in Sec. II with the help of three exactly soluble models. Finally in Sec. III we extrapolate from these particular examples in two directions: the stochastic aspect of statistical mechanics, and some remarks on the theory of the quantum measurement process. The presence, at the Symposium, of several distinguished lecturers who presented their own original, and most interesting, contributions hopefully made appear less outrageous - at least at the time - the severe omissions due to the personal choices this particular speaker had to make to keep within the time limitations inherent to such a gathering. It is now hoped that, even when taken out of the full context of the Symposium, the rearranged text which follows might nevertheless help focusing attention on some of the important problems remaining to be solved. It is a pleasure to acknowledge here the stimulating hospitality of the Symposium Scientific Director, Professor P.-O. Löwdin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170111
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  • 8
    Electronic Resource
    Electronic Resource
    Semigroups and the density matrix formulation of quantum mechanics (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 121-132 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A formulation of quantum mechanics is presented based on the theory of semigroups and the associated enveloping algebras of functions defined on countable subsemigroups. The existence of a unique *-involution is not assumed. The fundamental elements of a semigroup are identified with experimental precedures for the separation of subensembles from a given ensemble of experimental systems. Observables are represented as elements of enveloping algebras, and ensembles as density matrices within an enveloping algebra. The statistical properties of ensembles are expressed in terms of traces defined on the semigroup and its enveloping algebras. The elements and generators of the Poincaré group can be defined and interpreted in the usual way. A variety of applications is described, in which the theory of the density matrix plays an essential or effective role. Advantages associated with the resulting freedom from the limitations of Hilbert space are illustrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170112
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  • 9
    Electronic Resource
    Electronic Resource
    Nodeless wave function quantum theory (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 133-137 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nodes where the wave function changes sign in conventional quantum theory can alternatively be regarded as places where the wave function descends to zero but rises again without changing its sign. This behavior is accomplished by adding delta function barriers to the potential energy wherever a node occurs in the wave function. This model is supported by the recognition that the wave functions of a subsystem, which is not truly isolated, are really marginal amplitudes which implicitly average out interactions of the system with its environment. The finite effect of these interactions is to replace the delta function barriers by barriers of finite width and height.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170113
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  • 10
    Electronic Resource
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    Comments on the exclusion-principle-violating diagrams cancellation in correlations energy calculation by many-body Rayleigh-Schrödinger perturbation theory (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 195-209 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When calculating the correlation energy where the effect of higher than double excitations is included by means of many-body Rayleigh-Schrödinger perturbation theory (MB-RSPT) through fourth order the problem of cancellation of exclusion-principle-violating (EPV) diagrams arises. The cancellation of EPV diagrams in fourth order of MB-RSPT is demonstrated for diagrams which include the effect of tetraexcitations.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/qua.560170205
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  • 11
    Electronic Resource
    Electronic Resource
    Perturbative configuration interaction using localized orbitals in the INDO hypothesis. I. Theory and applications to energetical problems (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 211-233 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A complete development of the PCILO method is presented for the INDO approximation. The introduction of exchange terms in the theoretical treatment is discussed and a detailed analysis of the successive contributions to the total energy is given. The method is applied to various conformational problems (geometry optimization, rotation, and inversion barriers). Its ability to deal with biological systems is tested on the acetylcholine neurotransmitter. Inversion barriers are highly improved with respect to the corresponding CNDO algorithm. A better account of σ-π exchange phenomena can be expected with the presented PCILO-INDO development.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560170206
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  • 12
    Electronic Resource
    Electronic Resource
    Approaches for interpreting π electronic states and π electronic transitions (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 235-253 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Scope and limitations of different approaches which enable π electronic systems of topologically equivalent structures to be compared have been examined. Particular attention has been paid to analyses in terms of molecular subsystems.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560170207
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  • 13
    Electronic Resource
    Electronic Resource
    Resonances in the elastic electron-SF6 molecule scattering (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 255-263 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In agreement with previous calculations by the authors, three definite resonances in the elastic electron-SF6 molecule scattering in the energy range 5-40 eV have been obtained with a multiple scattering method, elaborated originally for molecular bound states and modified here for scattering states. Results with various more-reliable one-electron potentials have been compared with previous calculations and available experimental data.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560170208
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  • 14
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    Realization of the elementary biological function as a localized electron subsystem interaction processPresented at the International Conference on Quantum Chemistry, Biology, and Pharmacology held at Kiev, U.S.S.R., September 1978. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 265-272 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: While regarding the elementary biological function as a series of elementary acts resulting in either chemical bond formation (breakage) or a changed molecular subsystem state, we would like to focus attention on some of the most essential and general features of this process in terms of the Von Neumann theory of self-reproducing automata.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170209
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  • 15
    Electronic Resource
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    Electron mechanism of nonequilibrium molecular vibration excitation in biological systemsPresented at the International Conference on Quantum Chemistry, Biology, and Pharmacology held at Kiev, U.S.S.R., September 1978. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 273-283 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electron mechanism of the nonequilibrium vibration excitation is considered in multiatom molecules with the condition that the bottleneck effect takes place. The quantum-statistical theory states that if the simplest enzyme reaction is proposed on the basis of the vibrational energy recuperation idea, the vibrons emitted in producing the free product and enzyme activate the first stage of the formation of the Michaelis-Menten complex and the multiphonon feedback mechanism is realized. Resulting solutions are applied to explain some biochemical and genetic effects.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560170210
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  • 16
    Electronic Resource
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    Electronic absorption and emission spectra of nucleic acids and their components: Some questions of theory and experimentPresented at the International Conference on Quantum Chemistry, Biology, and Pharmacology held at Kiev, U.S.S.R., September 1978. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 307-320 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The results of calculations of the transition energies and polarization in nucleotide bases performed by the CNDO/S CI method are compared with experimental data for long-wavelength and vacuumabsorption bands. The calculations and the analysis of experimental data testify to the existence of n - π* transitions in the first absorption bands of the bases. The study of double-stranded polynucleotides and DNA hypochromism based on the theoretical electronic characteristics of the bases and perturbation theory is performed. The role of stacking and complementary interactions within the hypochromic effect is cleared up. Two mechanisms for the shift of the fluorescence band maximum are investigated: two-proton transfer along H bonds and excimer formation. The study of H-bond potential curves shows the disadvantage of two-proton phototautomerism in the nucleotide base pairs in contrast to model systems. The possibility of excimer state formation in stacked homo- and heterodimers of nucleotide bases is shown within the extended-Hückel treatment. The nature of excimer minimum for the excited-state potential curve is analyzed.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170214
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  • 17
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    Determination of potential-energy surface of molecules in an applied field on the basis of virial relationsPresented at the International Conference on Quantum Chemistry, Biology, and Pharmacology held at Kiev, U.S.S.R., September 1978. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 327-338 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The quantum-mechanical virial theorem (in diagonal and nondiagonal forms) for molecules in an external, weak, uniform electric field is used for obtaining the analytical expression of the potentialenergy surface in the Hartree-Fock-Roothaan one-determinantal approximation. The polarizability tensor components of the H2O molecule are computed on this basis. The dependence of basing the atomic orbitals upon the intensity of the applied field lead to good coincidence of results with the data of near Hartree-Fock calculations.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/qua.560170216
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  • 18
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    Conformational studies of double-helical polynucleotides by the method of pair-wise potential functionsPrepented at the International Conference on Quantum Chemistry, Biology, and Pharmacology held at Keiv, U.S.S.R., September 1978. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 321-326 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Double-helical polynucleotide conformations, poly(dA)·poly(dT), poly(d(A-T))·poly(d(T-A))·poly(dG)·poly(dC), and poly(d(G-C))·poly(d(C-G)) are analyzed by the atom-atom potential method. The energy optimization is carried out in the space of eight independent geometric parameters using analytical procedures for the constraints, taking into account the flexibility of the β-D-deoxyribose rings. At the first stage, the full screening of atomic partial charges was assumed. The structures of the calculated B and the A forms of DNA are characterized by low energy and absence of short contacts; the dihedral angles are near the average values in the monomers. With the typical energy difference of 3-5 kcal/mol nucleotide pairs in all cases, the B form is more preferable as compared to the A form. At the final step the effect of the Coulomb term is evaluated for poly(dA)·poly(dT) using various values of the effective dielectric constant (ε = 28, 24, 20, 18, 14, 12, 10, 8, 6, 4, and 1). If ε ≤24, the energy optimization leads A to B. We discuss the stereochemical details of the intermediate conformations on the A-B path and hypothesize the nature of stability of the A and the B forms and the mechanism of the A-B transition.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/qua.560170215
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  • 19
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    Interactions and self-organization of nucleic bases, nucleotides, and polynucleotides into ordered structures. Effect of ionization and solvent salt compositionPresented at the International Conference on Quantum Chemistry, Biology, and Pharmacology held at Kiev, U.S.S.R., September 1978. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 339-359 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper summarizes our findings on the effects of protons and neutral salt ions on intermolecular interactions and the self-organization of nucleotide systems in aqueous media, both at monomer and polymer levels. To gain quantitative information about these processes, methods were developed to determine the thermodynamic parameters of monomer association from the data obtained by various experimental techniques (NMR, UV spectroscopy, and spin labeling) and to estimate the individual contributions of base stacking and H-bonding in ordered structures of polynucleotides and their complexes. The main results obtained using these methods are as follows. (i) A difference was discovered in the effects of positive and negative charges on the stacking interaction between ionized and neutral molecules of nucleic heterocycles. Protonation strongly decreases the heterocycle ability to form ordered stacks whereas deprotonation slightly affects stacking. (ii) Base-phosphate interaction, which has not yet really been investigated, was studied. This interaction, along with base stacking, governs nucleotide association in water media. It appears upon protonation of the base moiety and increases with decreasing ionic strength. (iii) Base stacking was found to become stronger under the action of salt anions stabilizing the water structure and it became weaker under the action of destabilizing salt anions, both in monomer and polymer systems, which is indicative of an indirect mechanism of the anionic effects. It is essential that small salt ion additives acting by such a “distance” mechanism can affect the formation of ordered structures in nucleotide systems as strong as the direct interaction of the bases with protons. (iv) The results obtained suggest that an increase in solvent entropy upon the self-organization of nucleotide systems in aqueous media may be an important factor promoting these processes. (v) As follows from our data, specific weakening or strengthening of intermolecular interactions by protons and salt ions at small, physiological-range changes in pH or solvent salt composition seems to be an effective regulatory mechanism for the functioning of nucleotide systems.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560170217
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  • 20
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    Intensities of spin-forbidden transitions in molecular oxygen and selective heavy-atom effectsPresented at the International Conference on Quantum Chemistry, Biology, and Pharmacology held at Kiev, U.S.S.R., September 1978. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 367-374 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Intensities of a1Δg←X 3∑g- and b 1∑g+ ← X 3∑g- transitions in molecular oxygen have been calculated on the basis of the INDO method taking into account spin-orbit coupling by perturbation theory. The transitions are magnetic dipole in nature. The first of them (a - X) steals its intensity from 3Πg-3∑g- and 1Πg-1Δg transitions, which are determined by the orbital angular-momentum operator. This source is not the principal one for the intensity of the second (b-X) transition. Its intensity is stolen principally from microwave transitions between spin sublevels of the ground 3∑g- state. The last source explains the large difference in intensities of the a-X and b-X transitions. Calculated oscillator strengths are in a good agreement with experiment. The same integrals that determine the intensity also determine the parameters of the spin Hamiltonian for the ground 3∑g- state. These parameters are in a good agreement with experiment also, showing the validity of the whole calculation. In a condensed phase the investigated transitions are enhanced by intermolecular exchange interaction. It is known that an external heavy atom (EHA) enhances the b-X transition of oxygen in solution, but does not influence the a-X transition. In the collision complex O2-EHA, which has a geometry without inversion symmetry, the microwave transitions between spin sublevels of the “3∑g-” state obtain electric-dipole moments, which are stolen from the charge-transfer transition. This mechanism explains the selective effect of EHA.
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    URL: http://dx.doi.org/10.1002/qua.560170219
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  • 21
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    Nonadditivity of interaction in water trimers (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 377-398 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The energy of (H2O)3 has been calculated for 29 geometrical configurations of the trimer using the SCF LCAO MO method and extended as well as minimal basis sets of Gaussian functions. For two configurations two intermediate basis sets have also been tested. The results show the nonadditive component of the interaction energy to be small. They also indicate that fairly reliable results for the trimer can be obtained using minimal basis sets and the counterpoise method to eliminate the basis set superposition error. The nonadditive contribution to the interaction energy is shown to be mainly due to the long-range induction interaction.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560170302
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  • 22
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    On the validity range of the qualitative theory of chemical reactivity (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 399-413 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An attempt is made to refine the physical background underlying qualitative quantum-chemical concepts that are an essential component of the modern theory of chemical reactivity. The energy of electron delocalization in a transition state (stabilization energy, SE) is used as a measure of chemical reactivity. Using Coulson's integral representation for bond order matrix enables one to present the Woodward-Hoffmann rules and the effects of conjugated substitutents as theorems for a Hückel SE in alternant systems. A part of the results are extended to heteroatomic systems. The validity of the present treatment is discussed in terms of the SCF PPP theory.
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    URL: http://dx.doi.org/10.1002/qua.560170303
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    Fock coordinate function method for separation of spin variables in transition density matrices (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 415-428 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Fock generating function method is employed for the separation of spin variables into two-particle transition density matrices. Their spatial components introduced by McWeeny are expressed through Schrödinger's coordinate wave functions. Some nontrivial integral relations between these components and the charge and transition spin density matrices are obtained. The interrelation between the mentioned spatial components and the Matsen-Poshusta symmetrized density matrices of an arbitrary spatial function is found.
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    URL: http://dx.doi.org/10.1002/qua.560170304
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    Interaction of methane molecules (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 429-448 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Potential-energy curves for CH4·CH4 have been calculated using the SCF LCAO MO method. Six different mutual orientations of the molecules have been considered and several basis sets have been employed. An analytical potential has been fitted to the computed energy values and used in a Monte Carlo calculation to yield a spherically averaged CH4·CH4 potential. The potential, if corrected for dispersion interaction, agrees fairly well with that derived from thermophysical data. At short distances it disagrees with the potentials derived from scattering experiments which, however, are also incompatible with the experimental potential for large distances.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560170305
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    Two useful identities involving spherical harmonics (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 459-465 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present two identities that permit a simplification of some lengthy derivations with spherical harmonics. Examples of their use are given.
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    URL: http://dx.doi.org/10.1002/qua.560170307
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    Resonance energy of very large benzenoid hydrocarbonsThis paper is dedicated to Professor Linus Pauling. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 549-586 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The resonance energy of conjugated benzenoid systems is expressed as contributions arising from independent conjugated circuits. The scheme has been applied to numerous very large conjugated systems. In many cases, it was possible to find regularities in the increments for the resonance energy within a family of benzenoid systems as the number of benzene rings is increased.
    Additional Material: 15 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560170314
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    Polarization effects in photosynthetic membranesPresented at the International Conference on Quantum Chemistry, Biology, and Pharmacology, held at the Institute for Theoretical Physics, Kiev, U.S.S.R., 18-22 September 1978. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 587-593 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper investigates the polarization effects associated with functional processes in photosynthetic membranes.
    Additional Material: 6 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560170315
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    Books Received (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 596-596 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170317
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    Active-site α-helix in papain and the stability of the ion pair RS- ··· ImH+. Ab initio molecular orbital study (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 651-671 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio MO calculations, using both minimal (STO-3G) and extended (Roos-Siegbahn) basis sets are reported for the systems methanethiol-imidazole, methanethiol-imidazole-formaldehyde, and methanethiol-imidazole-formamide, which, together with a point-change representation of a long α-helix, form models for the active site of papain. It is shown that the large electric field exerted by the helix in the active-site region is responsible for the presence of the essential residues Cys 25 and His 159 in the form of an ion pair RS- ··· ImH+, which is crucial for a recently proposed mechanism for the catalytic action of the enzyme. Also, an explanation is given for the anomalies in measured pK values for these residues. Detailed studies on the (sub)systems show that minimal basis sets lack the flexibility necessary for describing the type of proton transfer involved. We conclude that α-helices are essential parts of enzymes and that they play a significant role in the catalytic process.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560170407
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    Use of the Hiller-Sucher-Feinberg identity for spin-density calculations (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 689-695 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The identity recently presented by Hiller, Sucher, and Feinberg relating the expectation value of a δ-function operator to that of another operator is rederived for the case of the Fermi contact interaction and the required expectation values expressed in terms of the spin-density and conditional spin-density matrices. The ground state of the H atom is considered as an example and it is shown that, for approximation by a linear combination of Gaussian orbitals, use of the identity improves the estimate of spin density at the nucleus by an order of magnitude or more.
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    SCF Theory of multiplet states (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 725-736 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The SCF theory of multiplet monodeterminantal states is described from a comprehensive viewpoint. In this context, the formalism and derived theorems are developed, as well as the description of a SCF closed-shell-like structure, namely the hypermultiplet. Numerical applications are discussed taking as a model the H2O molecule and its first positive ion. Wave functions of double ζ-quality, with computed molecular properties of 16 states are given.
    Additional Material: 3 Tab.
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    URL: http://dx.doi.org/10.1002/qua.560170413
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    Ab initio calculation of ESCA satellite intensities for a copper-chlorine complex (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 719-724 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio SCF calculations carried out on the planar cluster CuCl42- suggest that the strong satellites at the high-binding energy side of inner-shell ESCA lines of Cu are due to charge relaxations in the σ-bonding orbitals which mix with Cu 3d. The satellite state with the largest intensity may be described as a one-electron excitation Cu 3d → Cl 3p.
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    URL: http://dx.doi.org/10.1002/qua.560170412
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    Density of non-Bloch electron states in perfect cubic crystals (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 697-718 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper gives an abbreviated method for the calculation of the density of states of a crystal on the basis of that band theory in which the crystal electron states are represented by the standinglike wave functions classified according to the point-group symmetry species. The crystal is a large but finite sphere filled regularly with atoms, and the wave functions are quantized at the boundary of the sphere. The Bloch theorem is not satisfied in this theory since the wave functions are not basis functions of the irreducible representations of the translation subgroup. On the other hand, a theorem is established that the density of states can be made up of contributions given by all irreducible representations of the crystal point group, any contribution being proportional to the square of the dimension of the irreducible representation. In distinction to a former approach, the band structure is calculated solely from the energy eigenvalues obtained with the aid of the diagonalization process of the Wannier-Slater differential operator. A simple cubic lattice with an s atomic orbital on each lattice site is taken as an example, and the results are compared with Bloch's theory.
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    Slater-orbital molecular integrals by numerical Fourier-transform methods. II. Four-center integrals over is orbitalsPresented in part at the Microsymposium on Quantum Chemistry, Starý Smokovec, Czechoslovakia, 1977. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 747-757 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The four-center nonplanar electron repulsion integrals over 1s Slater-type atomic orbitals are considered by a numerical Fourier-transform method. It is shown that the highly oscillating integrand appearing in the Fourier inversion formula could be successfully treated by using Tchebyscheff quadrature. The resulting formulas are thoroughly discussed with particular emphasis on their numerical features and convergence properties. It follows that the aforementioned integrals may be calculated with a good accuracy with a moderate amount of computing time.
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    URL: http://dx.doi.org/10.1002/qua.560170415
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    Behavior of the electron density near an impurity (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 799-801 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The behavior of the electron density n(r) and potential energy V(r) near the origin, where an impurity of charge Z is located, is studied using the Lindhard dielectric theory of the free-electron gas. The leading odd terms in the power-series expansion of n(r) and V(r) are obtained. It is shown that the derivative n′(0) = -2Zn0/a0, where n0 is the free-electron gas density and a0 is the Bohr radius.
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    URL: http://dx.doi.org/10.1002/qua.560170418
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    Masthead (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560170501
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    Investigation of tertiary structure of a series of DNA compact forms by the small-angle X-ray scattering methodPresented at the International Conference on Quantum Chemistry, Biology, and Pharmacology held at Kiev, U.S.S.R., September 1978. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 813-817 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This work describes the investigation of the space organization of DNA compact forms and DNA-protein complexes by the small-angle x-ray scattering method. A plane texture was disclosed in dehydrated DNP films. Compact DNA particles formed in the presence of poly(ethylene glycol) reveal ordered structures having a periodicity of 84 Å. Various morphological forms of crystals of CTA-DNA were used to obtain small-angle x-ray patterns of the single-crystal type.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560170420
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    Absorption UV spectroscopy and electronic structure of ionic and tautomeric forms of hydroxy and methoxy derivatives of cytosine and adenine, and of some 5-substituted analogs of pyrimidinesPresented at the International Conference on Quantum Chemistry, Biology, and Pharmacology held at Kiev, U.S.S.R., September 1978. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 803-811 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The individual absorption spectra of various ionic and tautomeric species of some derivatives of nucleic-acid components have been determined by computer handling of the summary spectra of these compounds measured at different pH values. These individual spectra have been decomposed into separate bands represented by log-normal curves and corresponding to different electronic transitions. Using the parameter system calculated earlier for the molecules of the vitamin B6 family, the calculation of the electronic spectra and electronic structure of various ionic and tautomeric species of the molecules studied have been carried out in the π-electron approximation. These properties have also been calculated by the all-valence electronic method CNDOS. The calculated results correlate well with both approximations and with our experimental spectral data. The localization of the molecular electronic excitation studied on the transition to the S1 and T1 states is considered in connection with the reactivity in these states.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560170419
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    Topological characterization of cyclic structures (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 845-893 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sum of the topological distances in the molecular graph (the Wiener number) is used for a topological characterization of the condensed polycyclic molecular systems. This topological index discriminates well the isomeric cyclic molecules. In addition, it also properly reflects their structural features. On this basis the principal points of molecular cyclicity are formulated in 15 rules.
    Additional Material: 8 Ill.
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    Incomplete basis set problem. IV. Perturbative corrections to pair energiesThis research was supported by a grant from the Research Corporation. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 895-905 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A partitioning of the molecular Hamiltonian into the occupied and virtual orbital spaces and their orthogonal complement is introduced and used to develop a perturbation expansion of the exact ground-state energy relative to the Hartree-Fock energy computed using an incomplete basis set. The leading perturbation corrections to pair energies due to using the incomplete basis set are considered in detail. Summations of certain classes of pair contributions are discussed and a resummed correction is obtained.
    Additional Material: 7 Ill.
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    Floating spherical Gaussian orbital model study of some hydrogen-bridged systems: LiBeH3, LiBH4, LiCH5, and BeBH5 (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 907-914 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The floating spherical Gaussian orbital (FSGO) method has been used to study the equilibrium geometries and electronic structures of some hydrogen-bridged systems containing lithium, beryllium, boron, and carbon. The predicted geometries are in good agreement with other theoretical estimates. The binding energies for these hydrogen-bridged systems are estimated and discussed. The FSGO total energies (EFSGO), for all systems studied here, are found to be well correlated to nuclear-nuclear repulsion (Vnn) and nuclear-electron attraction (Vne) terms by a relation of the type EFSGO =\documentclass{article}\pagestyle{empty}\begin{document}$ {\textstyle{3 \over 7}} $\end{document} (2 Vnn + Vne).
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    Energy levels for perturbed Morse oscillators (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 931-942 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The energy levels and perturbation expansions for the expectation values of arbitrary powers of position for a perturbed Morse oscillator are obtained by application of the hypervirial and Hellmann-Feynman theorems, solely in terms of the unperturbed energy. We obtain expressions for the first-order corrections for (1 - e-aq )m for 4 ≤ m ≤ 8 and the expressions to second and third order for the quartic perturbation. A numerical application to the CO molecule is made.
    Additional Material: 9 Tab.
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    Global analysis of composite particles (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 915-930 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The theory of vibrations of a composite particle when vibrational amplitudes are not constrained to be small according to the Eckart conditions is developed using the methods of differential topology. A global classical Hamiltonian appropriate for this system is given, and for the case of the molecular vibration-rotation problem, it is transformed into a global quantum Hamiltonian operator. It is shown that the zeroth-order term in the global Hamiltonian operator is identical to the Wilson-Howard Hamiltonian; higher-order terms are shown to give successively better approximations to the large amplitude problem. Generalized Eckart conditions are derived for the global classical Hamiltonian; the quantum equivalent of these conditions along with the quantum equivalent of the Eckart conditions are given. The spectrum of the global Hamiltonian operator is discussed and it is shown that the calculation of the vibration-rotation energy states of the system reduces to the same straight-forward procedure, the solution of a secular determinant, as was carried out for the Wilson-Howard Hamiltonian at a later time by Nielsen.
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    High accuracy wave functions and eigenenergies for vibration-rotation states of diatomic molecules (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 943-954 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A solution of the wave equation for the rotational-vibrational motion in diatomic molecules with a new exponential potential function is carried out in detail. The solution gives simple expressions for the wave functions, eigenenergies, and other related spectroscopic constants. With these expressions Franck-Condon factors for the R branches of the A 1∑u--X 1∑g+ band system of Ca2, have been calculated which are in excellent agreement with experiment. Various strengths and weaknesses of the present method are also discussed.
    Additional Material: 1 Ill.
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    Approximate theoretical determination of molecular static polarizabilities (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 955-968 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular polarizabilities are computed using ab initio SCF wave functions and second-order perturbation theory with special attention given to the use of a shifted denominator. Rather small basis sets are used, in order to obtain reasonable values at a reduced cost. Results are presented for H2, CO, H2O, C2H4, OCS, C6H6, Cl2, Br2, I2.
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    Gaussian expansions of hydrogenic functions involving few variational parameters (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 1099-1109 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Des développments gaussiens complètement optimisés des fonctions hydrogénoïdes de type 1s, 2pz, 3dxy, et 4fxyz ont été pratiquement reproduits par une construction spéciale des paramètres variationnels. L'utilité des fonctions génératrices utilisées est discutée brièvement.
    Abstract: Vollständig optimisierte Gaussentwicklungen wasserstoffähnlicher Funktionen von Typ 1s, 2pz, 3dxy, und 4fxyz sind mittels eines speziellen Verfahrens für die bestimmung der Variationsparameter praktisch reproduziert worden. Der Nutzen der angewandten erzeugenden Funktionen wird kurz diskutiert.
    Notes: Fully optimized lengthy Gaussian expansions of hydrogenic 1s and 2pz functions have been practically reproduced by generating the variational parameters by means of suitably chosen functions involving only few parameters. Hydrogenic 3dxy and 4fxyz functions have been approximated in a similar way. The usefulness of such generating functions is briefly discussed.
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    URL: http://dx.doi.org/10.1002/qua.560170606
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    Ab initio calculations on large molecules using molecular fragments. Generalization of the molecular fragment basis at the minimum basis set levelSupported in part by the Division of Basic Energy Sciences of the United States Department of Energy, and the Upjohn Company, Kalamazoo, Michigan. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 1075-1097 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: En déterminant les paramètres des jeux de base dans des environnements moléculaires par d'autres critères que l'énergie totale, il est démontré qu'une généralisation de la base pour des fragments moléculaires peut ětre obtenue, dans laquelle les propriétés géométriques et celles de la structure électronique sont prédites considérablement mieux qu'avec des bases de taille semblable. Comme premier pas dans le développement d'une série de bases avec une flexibilité et une précision de plus en plus prononcée, on a construit plusieurs jeux de base de type simple zéta avec une contraction gaussienne pour chaque orbitale de base. Les meilleures de ces bases donnent des propriétés géométriques et électroniques pour une série de molécules organiques avec'une précision meilleure que celle obtenue par la base correspondante de type STO-2G et semblable dans la plupart des cas à STO-3G. En outre cette base peut ětre utilisée soit avec des gaussiennes cartésiennes, soit avec des gaussiennes sphériques flottantes.
    Abstract: Durch eine Bestimmung von Basissatzparametern in Molekülumgebungen mit anderen Kriterien als der Gesamtenergie wird gezeigt, dass eine Verallgemeinerung des Molekülfragmentsbasissatzes erhalten werden kann, mit welchem geometrischen und Elektronstruktureigenschaften beträchtlich besser als mit anderen Basissätzen ähnlicher Grösse vorhergesagt werden können. Als erster Schritt in der Entwicklung einer Reihe von Basissätzen mit sukzessiv grösserer Flexibilität und Genauigkeit werden mehrere Basissätze von Einzelzetatyp durch eine Gauss'sche Kontraktion für jedes Basisorbital konstruiert. Mit den besten dieser Basissätze werden geometrische und elektronische Eigen-schaften für eine Reihe von organischen Molekülen mit besserer Genauigkeit als dem entsprechenden STO-2G Basissatz und in vielen Fallen ähnlich dem STO-2G Satz erhalten. Weiter wird gezeiget, dass dieser Basissatz mit sowohl Cartesischen als fliesseden sphärischen Gaussfunktionen vereinbar ist.
    Notes: By determining basis set parameters in molecular environments using other criteria than total energy, it is shown that a generalization of the molecular fragment basis can be obtained in which calculated geometric and electronic structural properties are predicted substantially better than with other basis sets of similar size. As a first step in the development of a series of basis sets having successively greater flexibility and accuracy, several single-zeta basis sets are created, using a two-Gaussian contraction for each basis orbital. The best of these basis sets produced calculated geometric and electronic properties for a series of molecules that model a wide variety of organic molecules that are of better accuracy than the corresponding STO-2G basis, and similar in most cases to STO-3G. In addition, the basis set is shown to be applicable in either a Cartesian Gaussian basis or a floating spherical Gaussian basis.
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    Projected surface energy bands, Shockley surface states, and bonding in transition-metal monocompounds with rock-salt structure: Example of NbC (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 1167-1177 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: La théorie qualitative des états de surface de Shockley est utilisée pour discuter l'existence d'états de surface sur trois faces du carbure de niobium: (001), (011), et (111). Les résultats obtenus pour NbC sont généralisés pour inclure d'autres composés de métaux de transition MX, X = C, N, O. Les états de surface dans les matériaux de ce type-là sont importants pour la chemisorption et la catalyse. La théorie qualitative des états de Shockley paraǐt ětre utile pour voir des effects de covalence forte dans les solides.
    Abstract: Die qualitative Theorie der Schockley'schen Oberflächenzustände wird angewandt um die Existenz von Oberflächenzuständen auf drei Flächen von NbC: (001), (011) und (111) zu diskutieren. Die für NbC erhaltenen Resultate werden zu anderen einfachen Übergangsmetallverbindungen, MX, X = C, N, O. verallgemeinert. Oberflächenzustände in solchen Verbindungen sind für Chemisorption und Katalyse wichtig. Die qualitative Theorie der Shockleyzustände scheint für die Analyse von starken kovalenten Effekten in Festkörpern nützlich zu sein.
    Notes: The qualitative theory of Shockley surface states is used to discuss the existence of surface states on three faces of niobium carbide: (001), (011), and (111). The results obtained for NbC are generalized to include other simple transition metal compounds MX, X = C, N, O. Surface states of these and related materials are of interest in chemisorption and catalysis. The qualitative theory of Shockley states appears to be useful tool in detecting strong covalency effects in solids.
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    Behavior of molecular potential energy curves for large nuclear separations (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 17 (1980), S. 1143-1166 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Nous prouvons par des méthodes géométriques élémentaires et dans le cadre de l'approximation de Born-Oppenheimer, que quand les noyaux d'une molécule sont dissociés en amas séparés dans l'espace, les énergies moléculaires discrètes tendent vers la somme des énergies des sous-systèmes isolés. Nos méthodes montrent aussi que les projections spectrales associées au spectre moléculaire discret tendent asymptotiquement vers des sommes directes de projections spectrales convenables pour les sous-systèmes isolés. Ces résultats s'appliquent à n'importe quel système de particules qui interagissent par des potentiels de paire s'annulant asymptotiquement. Nous prouvons que le développement en 1/R pour des courbes de potentiel moléculaires discrètes est asymptotique quand R → ∞, et nous discutons le comportement des coefficients de ce développement pour l'état fondamental de H2+.Wir beweisen durch elementare geometrische Methoden und im Rahmen der Born-Oppenheimer-Näherung, dass, wenn die Kerne eines Moleküls in räumlich separierten Clusters dissoziiert werden, die diskreten Molekülenergien Summen der Energien der isolierten Untersysteme zustreben. Unsere Methoden zeigen auch, dass die mit dem diskreten Molekularspektrum assoziierten Spektralprojektionen asymptotisch direkten Summen von geeigneten Spektralprojektionen für die isolierten Untersysteme zustreben. Diese Ergebnisse sind für irgendein System von Teilchen gültig, die durch asymptotisch verschwindende Paarpotentiale wechselwirken. Wir beweisen, dass die Entwicklung in 1/R für diskrete molekulare Potentialkurven wenn R → ∞ asymptotisch ist, und wir diskutieren das Verhalten der Koeffizienten dieser Entwicklung für den Grundzustand von H2+.
    Notes: We prove by elementary geometric methods and within the Born-Oppenheimer approximation that as the nuclei of a molecule are dissociated into spatially separated clusters, the discrete molecular energies approach sums of the energies of isolated subsystems. Our methods also show that the spectral projections associated with the discrete molecular spectrum asymptotically approach direct sums of suitable spectral projections for the isolated subsystems. These results apply to any system of particles interacting by asymptotically vanishing pair potentials. We prove that the 1/R expansion for discrete molecular potential curves is asymptotic as R → ∞, and we discuss the behavior of the coefficients of the 1/R expansion for the ground state of H2+.
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    Ab initioLCAO MO SCF calculation of potential surface of the NO2 molecule (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 151-156 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The SCF potential surface of the ground state for NO2 was calculated by using program JAMOL 3. The McLean-Loew-Berkowitz CGTO's were used as basis functions. One of the two N—O distance R is fixed to 2.25 a.u. and the other one r and the ONO angle θ are varied from 2.25 to 5.0 a.u. and from 0° to 180°, respectively. The potential surface has the minimum around r = 2.50 a.u. and θ = 120°, where the energy is found to be -203.954 a.u.
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    URL: http://dx.doi.org/10.1002/qua.560180121
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    Basis set superposition effect on difference electrostatic molecular potential contour maps (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 165-171 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560180123
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    Potential-energy surfaces in the lower excited states of benzene⇌Dewar-benzene isomerization process (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 157-164 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Adiabatic potential-energy surfaces in the lower excited states following the benzene⇌Dewar-benzene isomerization process were calculated by the INDO/S method postulating the concerted reaction mechanism which is proved to be valid in the ground state by the calculation of the intrinsic reaction coordinate. It was concluded that the benzene molecule in the 1B1u and 1E2u excited states readily isomerizes to Dewar-benzene in the condensed phase although the quantum yield may not be large. Bryce-Smith's proposal, that the isomerization to Dewar-benzene occurs only after the intersystem crossing to the 3B1u state in benzene molecule, will not be probable; for the 3B1u route is not favorable to the isomerization in comparison with these singlet routes. However, the rearomatization of Dewar-benzene in the ground state may produce the 3B1u benzene in small yield with higher yield of the ground-state benzene. The activation energy in the rearomatization is calculated to be 19.03 kcal/mol. These conclusions are consistent with the experimental facts. Molecular orbital correlations in the isomerization and the ionization potentials of Dewar-benzene were also discussed.
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    Field correlation effects on the resonant light scattering (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 293-300 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Effects of incident photon field coherence on resonant light scattering have been investigated. In order to obtain the scattering intensity and the photon counting rate, an expression for the reduced density matrix for the scattered field has been derived. The expression involves the first-order correlation function of the incident field. The relation between the line shape of the scattered light and the bandwidth of the incident field has been clarified. Model calculations of the photon counting rate have been performed in the case of an incident field without first-order coherence. In our treatment, the transverse and longitudinal relaxation constants have been taken into account by using the impact approximation.
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    Relativistically parametrized extended-Hückel calculations. II. Orbital energies of group-IV tetrahalides and tetramethyls (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 347-355 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Relativistically parametrized extended-Hückel (REX) calculations are reported for MX4 (M = Ti, Zr, Hf, C, Si, Ge, Sn, Pb; X = Cl, Br, I) and for M(CH3)4 (M = Ti, C, Si, Ge, Sn, Pb). Satisfactory agreement is obtained with experiment and with earlier assignments both for the energy levels and for their relativistic splittings. This encourages the use of REX for assigning PES spectra. Double-ζ radial functions (REX and EHT) are given for Cl, Br, and I.
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    INDO Studies on the structure of benzosemiquinone radicals (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 357-363 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The spin densities of the radical anions from 4-methylcatechol, 4-carboxylic catechol, and 3-methylcatechol were calculated by means of the INDO method with the geometrical parameter adjusting method. The observed protion hyperfine coupling constants were exactly reproduced.
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    Assignment of the hyperfine constants of the 1,2-benzosemiquinone radical anion: Comment on “INDO studies on the structure of benzosemiquinone radicals”By Y. Shinagawa et al., preceding paper. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 365-367 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/qua.560180205
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    Chemical graph theory: Modeling the thermodynamic properties of molecules (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 369-380 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Graph- and information-theoretical indices were recently developed as quantitative structural characteristics of molecules. In this paper they are found to correlate well with a number of molecular properties of alkylbenzenes: heats of formation, combustion (both in liquid and gas phase) and vaporization, molecular volume, boiling point, and parachor. The topological information index and the number of carbon atoms are taken as variables. The correlation coefficient was found to be equal or close to 1. In three cases the mean relative error is less than 0.1%, in another three cases it is within the range 0.2-0.4%, and for boiling points only it is 1.25%. The proposed approach is compared with the additive scheme of Tatevskii.
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    MO Study of flavin-protein interactions in flavodoxin catalysis (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 449-456 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: MINDO/3 calculations have been performed on the Clostridium MP flavodoxin active site (a complex of the redox active coenzyme flavin mononucleotide sandwiched between the side chains of methionine and tryptophan) at various redox levels using coordinates derived from x-ray diffraction studies of the holoenzyme. Frontier orbital indices were calculated and indicate that reduction of the flavin is accompanied by induced polar states in the amino acid side chains. This stabilization of charge by the amino acid side chains could account for the reaction rate enhancement of flavin reduction catalyzed by flavodoxin. Frontier orbitals for free flavin, for the flavodoxin bound flavin without the amino acid side chains, and for the oxidized Desulfovibrio vulgaris flavodoxin active site were computed for comparison.
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    Binding energies of ionized donor-exciton complexes in polar crystals (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 583-586 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Binding energies of ionized donor-exciton complexes in crystals of CdSe, CdTe, and ZnSe are calculated using the most realistic effective potentials available for the electron-hole interaction.
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    Electronic states near dislocations in transition metals: An application of quantum chemistry in technology (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 575-582 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper outlines a model for calculating the localized states of a 〈 100 〈 edge dislocation in α-Fe. The model used for the calculations is based on the multiple-scattering model (SCF-X α-SW). The purpose of this research is twofold: (1) To determine changes in electronic structure of the lattice near the core region of defects in α-Fe. (2) The variations of hydrostatic pressure about an edge dislocation produce a rearrangement of the conduction electrons. The question is what electrical interaction might be expected between a dislocation and a charged solute atom. The calculations show that the electrons tend to flow away from the compression side toward the dilated regions. The electrical contribution to the binding energy of a solute atom and a dislocation in α-Fe is of the order of 0.01 Ry/electronic unit charge of the atom.
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    Fluorescence spectra and their temperature dependence of amorphous anthracene films doped with naphthacene (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 587-593 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fluorescence spectra and their temperature dependence of amorphous anthracene films doped with naphthacene were observed. An amorphous film was prepared by vacuum evaporation technique on a quartz plate cooled down to 30-40°K. The obtained results were discussed in relation to the structural change in the amorphous film.
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    Nonadditive effects in metal clusters and chemisorption. Pseudopotential study of palladium clustersPresentation supported in part by Conacyt. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 595-600 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The analysis of nonadditive effects in small palladium clusters via LCAO-MO-SCF calculations using the nonempirical pseudopotential model is presented. The results are tentatively correlated with previous studies on various metal clusters (Li, Be, Mg, etc.) for which a good knowledge of multibody terms has provided a valuable guide for understanding the cluster stabilities and their chemisorption capacity.
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    N2 Laser-excited luminescence of antiferromagnetically coupled trinuclear chromium(III) complexes (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 625-631 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Exchange interaction parameters in several trinuclear chromium(III) complexes [Cr3O(R-COO)6(H2O)3]X·nH2O (R = CH3, C2H5) are determined in the study of luminescence, time-resolved luminescence (TRS), and decay time measurements over the temperature range 4-100°K. The presence of four inequivalent trinuclear clusters and a luminescence anomaly at 25 and 55°K are observed in the basic chromium(III) acetate prisms. Magnetic anomalies reported earlier should be attributed to the distortion and disordering of the hydrogen-bonded channels in crystals at low temperatures.
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    Lattice relaxation and electric-field-gradient calculations in impurity-doped single ionic crystals (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 633-640 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The lattice-relaxation parameters in several ionic crystals doped with monovalent impurity ions are calculated by energy minimization, taking into account the Coulomb, overlap-repulsive, and three-body potential energies. The displaced 256 ions around one substitutional impurity ion are taken into consideration and the results are utilized to calculate the electric-field gradients at sites similar to the (1,0,0), (1,1,0), and (1,1,1) sites relative to the impurity at (0,0,0), by using two different models for three-body potentials.
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    Rotational tunneling of methane on the surface of graphite (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 641-644 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Neutron scattering spectra from methane molecules adsorbed on a surface of graphite were observed by Newbery et al. They found four inelastic peaks in the temperature range lower than 30°K and assigned them to transitions between rotational tunneling states of methane molecules. This system was investigated by introducing both the interaction between methane molecules and that between a methane molecule and carbon atoms of graphite in order to explain the observed spectrum. It is shown that the system can be analyzed in terms of an effective field with tetrahedral symmetry.
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    Synchrotron radiation spectroscopy of quasi-one-dimensional materials (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 655-659 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The optical reflectivity spectra of quasi-one-dimensional polymers (SN)x, trans-(CH)x, and polydiacetylene are investigated in an energy range from 1 to 25 eV by use of synchrotron radiation. Observed structures associated with π-electron states are interpreted in terms of the quasi-one-dimensional one-electron bands calculated by the LCAO-type model.
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    Electronic spectra of nucleic acid bases: Variable electronegativity calculations and an analysis of existing results (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 827-840 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Variable electronegativity Pariser-Parr-Pople (VE-PPP) calculations have been carried out on the bases of nucleic acids and 5-fluorouracil. Directions of polarization for the various electronic transitions in these molecules have been calculated using the wave functions obtained by this and the CNDO/S-CI methods. The calculated excitation energies, oscillator strengths, and directions of polarization have been compared with the PPP results due to Pullman and co-workers and Bailey as well as the experimental ones. It has been found that a comparative study of this type is much more useful for understanding the transitions in the molecules than the individual calculations. The VE-PPP method is found to generally give the best results. The directions of polarization have been used to identify the transitions in the molecules and to compare the excitation energies obtained by different methods. It is shown that the transitions in these molecules do not have the characteristics of those of benzene derivatives. All the observed peaks in the molecules have been explained as π*→π.
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    Configuration interaction matrix elements. III. Spin functions relating the unitary and symmetric group approaches (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 841-866 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Spin functions that are compatible with orbital ordering and geminal antisymmetry conditions are investigated. It is shown that two widely used classes of spin functions, namely, the spin-bonded functions and Yamanouchi-Kotani (or, equivalently, Gelfand-Tsetlin) functions possess these properties. The relationship of the latter with Young-Yamanouchi spin functions is also outlined using graphical techniques of spin algebras. These techniques are also used to rederive the Hamiltonian matrix elements between spin-bonded functions and to show the relationship among the various schemes used in this case.
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    Variational constraints on perturbed eigenvalues and their perturbation expansions. II. Perturbational inequalities (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 867-890 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A large family of interlocking perturbational inequalities is derived by variational considerations for the stationary states of all systems described by a Hamiltonian linear in a real perturbing parameter λ. These inequalities constrain in many different ways the perturbation expansions of both exact and variational eigenvalues for these systems; analogous inequalities are derived for the components of the eigenvalues. A special feature of the analysis consists of obtaining inequalities applicable to the separate sums of even- and odd-order perturbation energies. For lowest states of each symmetry and for positive definite perturbing operator, the interlocking effect of the inequalities becomes extremely restrictive. The inequalities are illustrated with several numerical calculations for different systems and states of the helium isoelectronic sequence. The direction of the inequalities is found to be unaffected by low-order truncation, thus rendering them applicable to low-order perturbation expansions. The inequalities are used to study the efficacy of low-order perturbation theory for two- to ten-electron atomic isoelectronic sequences, and to determine the functional dependence upon λ of the eigenvalues and their components for arbitrary atomic isoelectronic sequences.
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    Role of CA2+ ion in the abortifacient action of prostaglandins. II. Molecular orbital and conformation energy calculations of PGA1 (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 891-904 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper reports some theoretical studies of PGA1 using conformational and molecular orbital techniques. The conformation energy (CE) calculations, using empirical potential-energy functions, for intrinsic torsional rotations around C12—C13 (θ), C7—C8 (Ψ), and C14—C15 (φ) show a number of energy minima. The relative value of the CE for these minima ranges from 4.09 to 8.01 kcal/mol. An additional rotation around C4—C5 (χ) giving “twist” to the carboxyl chains lowers the CE value by 2-3 kcal/mol and a conformation with CE value 2.39 kcal/mol less than crystallographic one is obtained. The interchain interaction energy showed changes with conformations. No significant change in the interchain interaction energy was observed due to “twist” in the carboxyl chain. The isopotential mapping study demonstrated the probable ionic binding site near the carboxyl and the ring (O9) oxygens. Conformational and molecular orbital results are discussed in the light of the reduced abortifacient potency of PGA1 with respect to PGF2α and the possible role of Ca2+ ions in this action.
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    URL: http://dx.doi.org/10.1002/qua.560180319
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    Fourth-order invariant in Rayleigh-Schrödinger perturbation theory (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 905-906 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/qua.560180320
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    Energy-eigenvalue sum relationship in molecules (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 907-909 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/qua.560180321
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    Electron correlation and Hund's rule (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 921-935 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is suggested that simple electronic shielding effects induced by wave function antisymmetrization tend to govern the energy ordering of singlet and triplet terms within a two-electron atomic configuration. This approach gives rise to the following alternating rule: For the term of greatest orbital angular momentum within a configuration, the triplet lies below the singlet. The energy ordering reverses for the term of next highest angular momentum, and continues to alternate with each change of one unit in the orbital angular momentum until the term of lowest angular momentum is reached. In an examination of over 600 energy levels of the elements and their ions, the alternating rule reliably orders singlet-triplet energy levels in some 90% of the cases.
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    Stable and efficient algorithms for Xα multiple scattering calculations (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 1091-1099 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solutions to some practical problems that arise in multiple scattering calculations on large molecules are discussed. (1) Numerical instabilities near the zero of energy can be removed by rescaling the secular matrix. (2) The calculation of structure factors can be made much more efficient by the application of symmetry projection operators. (3) An energy search procedure is described that ensures that no states are inadvertently neglected. Test calculations incorporating these changes illustrate the improved numerical stability, and show decreases in computation time of 30-60%, when compared to previous codes. The procedures suggested here are applicable to both relativistic and nonrelatitistic calculations.
    Additional Material: 2 Ill.
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    On Löwdin orthogonalization (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 1101-1108 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that the Löwdin orthogonalization gives the unique minimum for the functional φ measuring the least squares distance between the given orbitals and the orthogonalized orbitals. Furthermore a much stronger result is obtained, namely that φ has only one local minimum, which is attained at the Löwdin orthogonalization and which is global. This justifies certain computer programs that compute Löwdin orthogonalization via minimization procedures. Finally there is a discussion of replacing the least squares metric by other metrics. The Löwdin orthogonalization turns out to be optimal with respect to all the commonly encountered norms.
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    Self-consistent approximation to the polarization propagator (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 1109-1131 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A theorem is presented that characterizes approximate states and truncated operator manifolds associated with self-consistent approximate propagators. This theorem establishes a natural relationship between Hermiticity, stationarity, nonredundance and completeness of operator manifolds, model time evolution, and the vacuum condition. For the case of the polarization propagator we describe algorithms by which we can construct states and manifolds that satisfy this theorem and the vacuum condition.
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    Masthead (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560180501
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    High accuracy wave functions and eigenenergies for the vibration-rotation states of diatomic molecules by factorization method (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 1133-1142 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A solution of the wave equation for the nuclear motion of a diatomic molecule with an exponential potential function and the rotational term included has been performed by the Schrödinger-Infeld-Hull factorization method. Two different procedures have been followed for the factorization of the wave equation, and in each of them, as type-B factorization is incapable of producing wave functions, it has been transformed to type-C factorization, and a complete set of wave equations have been obtained. Of the two procedures, although the former appears to be more direct, the latter is the more accurate and generalized one.
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    Multiple scattering mass operator method for molecular orbital calculationsWork supported by the Brazilian agencies CNPq and FAPESP. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 1165-1173 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An exchange-correlation potential model to be used in connection with the multiple scattering method is presented. Retaining the main advantages of the multiple scattering method with the Xα potential, particularly its low computational requirements, this new formalism does not require any adjustable parameter. Test calculations on the NiF64- system are reported and compared with experimental and ab initio results.
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    Improved transformation algorithm of two-electron integrals from atomic orbital basis to a symmetry orbital basis (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 1157-1163 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transformation of two-electron integrals from an atomic orbital basis to a symmetry orbital basis is a straightforward procedure, but becomes a time-consuming process when the system has high symmetry. In the conventional transformation algorithm, the number of multiplications is proportional to the fifth power of the basis size. To reduce the computer time, a new transformation algorithm is proposed. In this method, the number of multiplications for the transformation is proportional to the fourth power of the number of atomic orbitals in an equivalent orbital group. A new transformation program has been completed and tested against the conventional n5 method. The present method may be regarded as extension of Almlöf's method to any molecular point group. The program cuts the CPU time for the transformation to one-third in calculations for C4H8 and NiF6. This reduction is quite significant for large systems having high symmetry.
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    Concept of charge transfer: Investigation of charge transfer in the glyoxal-formamide, water dimer, and water-lithium cation systems (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 1143-1155 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this paper an attempt is made to define charge transfer trying also other ways than Mulliken's population analysis. To illustrate this the amount of transferred charge (q) in the complexes HCONH2 + OHC - CHO in two relative geometrical positions, H2O + H2O and H2O + Li+ has been calculated with the help of Mulliken's population analysis using the wave function of the complex on the one hand and in the framework of different methods to subdivide the total space of the complex into subspaces for the acceptor and donor molecule, respectively, on the other hand. The results obtained show that Mulliken's population analysis gives a qualitatively correct description of the charge transfer process but to obtain the finer details most probably the use of a single number (q) is not sufficient. Further, the change in the total energy with respect to an effective charge transfer of a water dimer and of a solvent-cation complex has been investigated using the new mutually consistent field method. In this way the amount of transferred charge as well as the charge transfer interaction energy have been obtained in one step. These results have been compared with calculations applying second-order perturbation theory including overlap and the supermolecule method.
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    Inclusion of hydrogen p orbitals in the semiempirical calculation of NMR parameters. I. Influence on the FPT INDO spin-spin coupling constantsPart of a Ph.D. thesis (J.C.F.) to be presented to the University of Buenos Aires. (1980)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 18 (1980), S. 1175-1185 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogen 2p orbitals have been introduced into the basis set to calculate the Fermi contact term of spin-spin coupling constants using the FPT INDO method. Different coupling constants show different sensitivity to these hydrogen polarization functions. Some improvements are found for molecules containing N or F. Calculations of proton-proton geminal coupling constants give more negative results than those of FPT INDO, yielding a better agreement with experimental values. The π-transmission mechanism is notably exaggerated.
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    Foundations of the relativistic theory of many-electron bound statesDedicated to the memory of Geeta Udgaonkar, 1958-1982.Invited paper, Symposium on Relativistic Effects in Quantum Chemistry, Åbo Akademi, Turku, Finland, June 21-23, 1982. (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 3-21 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Most of the existing calculations of relativistic effects in many-electron atoms or molecules are based on the Dirac-Coulomb Hamiltonian HDC. However, because the electron-electron interaction mixes positive- and negative-energy states, the operator HDC has no normalizable eigenfunctions. This fact undermines the quantum-theoretic rationale for the Dirac-Hartree-Fock (DHF) equations and therefore that of the relativistic configuration-interaction (RCI) and multiconfiguration Dirac-Fock (MCDF) methods. An approach to this problem based on quantum electrodynamics is reviewed. It leads to a configuration-space Hamilton H+U which involves positive-energy projection operators dependent on an external potential U; identification of U with the nuclear potential Vext corresponds to use of the Furry bound-state interaction picture. It is shown that the RCI method can be reinterpreted as an approximation scheme for finding eigenvalues of a Hamiltonian H+U, with U identified as the DHF potential; the theoretical interpretation of the MCDF method needs further clarification. It is emphasized that if U differs from Vext one must consider the effects of virtual-pair creation by the difference potential δU = Vext - U; an approximate formula for the level-shift arising from δU is derived. Some ideas for dealing with the technical problems introduced by the projection operators are discussed and relativistic virial theorems are given. Finally, a possible scheme for adapting current MCDF methods to Hamiltonians involving projection operators is described.
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    Convergence problems in SCF calculations: Further applications of a new technique based on the use of inverse Fock operator (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 809-816 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A recently proposed orbital optimization technique based on the use of the inverse of the level-shifted Fock operator is successfully applied to a large number of pathologically divergent cases. The possibility of eliminating convergence problems by adopting a similar modification in the operation of the orthogonal gradient method is also successfully tested.
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    The band structure of porphyrinatonickel(II). A semiempirical crystal orbital study based on the tight-binding formalism (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 817-851 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The band structure of porphyrinatonickel(II) (2) has been studied by means of crystal orbital calculations that are based on the tight-binding approximation; the computational framework is a recently developed INDO model for transition metal compounds of the 3d series. The porphyrinato polymer has been studied in an eclipsed arrangement (2a) and in a staggered conformation (2b) where neighboring layers are rotated by 41°. The total energy of the metallomacrocycle has been decomposed into one- and two-center contributions; the latter interaction parameters have been fragmented into physically feasible resonance, exchange, and classical electrostatic (electron-electron, electron-core, core-core) interactions. It is shown that individual two-center potentials between atoms in neighboring layers are prevailingly determined by the electrostatic interaction energy. The NiNi coupling in the chain is highly repulsive; important stabilizing interactions are predicted between the 3d center of one cell and the electronegative N atoms in the neighboring layers. Stabilizing and destabilizing electrostatic interaction potentials largely compensate each other; the net stabilization in the polymer comes from the accumulation of resonance and exchange increments. The unoxidized Ni(II) porphyrinato polymer is an insulator. Several ligand bands (π, σ, and lone-pair) are predicted on top of bands with significant Ni 3d admixtures; the conduction band of the unoxidized strand is of ligand π* character. The dense manifold of ligand states in the vicinity of the Ni 3d states (3dz2, 3dx2-y2, 3dxz/3dyz) prevents the formation of bands in the polymer that are strongly localized at the 3d center. Ni 3dz2 and 3dx2-y2 interact strongly with ligand lone-pair and σ states. Avoided crossings between ∊(k) curves in k space lead to compositions in the various bands that differ significantly at the bottom and the top. The INDO crystal orbital formalism predicts a partial oxidation of ligand bands in derivatives of 2 that contain oxidants (e.g., halides). The theoretical findings derived for 2 are compared with available experimental data on highly conducting porphyrinatonicke(II) polymers (tetrabenzo and octamethyltetrabenzo derivatives of 2).
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    Numerical solution of Hartree-Fock equations for a polyatomic molecule: Linear H3 in momentum spaceThe French version has been submitted to the Comptes Rendus de l'Académie des Sciences. (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 863-867 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We give an example of multidimensional numerical solutions in momentum space, for the Hartree-Fock equations of the simplest molecule with more than two electrons and two nuclei.
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    The effect of an epoxide-nucleophile reaction upon hydrogen bonding involving the nucleophile (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 869-879 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The aim of this study has been to determine how the hydrogen bond between formaldehyde and ammonia is affected by the ring-opening interaction of protonated ethylene oxide with the ammonia nitrogen. Our purpose is to gain insight into the possible effect of carcinogenic epoxides upon the hydrogen bonding within DNA base pairs; it is known that such epoxides react with nucleophilic sites in DNA, including amine nitrogens that are involved in hydrogen bonds to carbonyl groups. We have used an ab initio self-consistent-field molecular orbital procedure to compute optimized structures, interaction energies, and other properties of interest. The H2CO·HNH2 system and the protonated epoxide were found to form two stable complexes, with syn and anti orientations. Their formation is accompanied by a significant overall strengthening of the H2CO·HNH2 hydrogen bond, as indicated by both calculated force constants and bond lengths. An analysis of these and other properties, such as atomic charges, suggests that the interaction is leading to the formation of N-protonated ethanolamine, which is linked to the formaldehyde through the proton on the nitrogen. If carcinogenic epoxides have a similar strengthening effect upon some of the hydrogen bonds in DNA, it could interfere in the replication and transcription processes.
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    Asymptotic analysis of exchange interactions (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 891-914 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The leading term in the asymptotic expansions of the three-center contributions to the exchange matrix elements for a system of three hydrogen atoms is derived. The approximations are used to estimate the importance of three center interactions in “spin-aligned hydrogen”.
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    Masthead (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984) 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1002/qua.560250601
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    Generalized Hellmann-Feynman and curvature theorems in classical and quantum mechanics (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 915-928 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The generalized Hellmann-Feynman and curvature theorems are derived for the generalized Sturm-Liouville-type eigenvalue equation which is widely encountered in many branches of physics. In classical mechanics, the Sturm-Liouville eigenvalue equation primarily arises from applying the theory of small oscillations to vibration problems while, in quantum mechanics, the most important example is the time-independent Schrödinger equation. The generalized theorems, respectively, provide simple useful expressions for the first and second λ derivatives of the eigenvalue where λ is an arbitrary real parameter appearing in the eigenvalue equation. These results, which apply to both classical and quantal systems, include as special cases the well-known quantum mechanical Hellmann-Feynman and curvature theorems for the time-independent Schrödinger equation, thus unifying the formalism. This connection between classical and quantum mechanics is of interest per se, and also because classical eigenvalue equations find application in the treatment of some quantum chemical problems. Two derivations of both generalizations are presented, the first proof applying to exact and Rayleigh-Ritz (linear variational) solutions of the eigenvalue problem, and the second, more general one, to arbitrary optimal variational as well as exact solutions. Necessary and sufficient conditions for the validity of the results are discussed. To demonstrate the insight they afford, several applications of the theorems in conjunction with perturbation theory are described.
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    On the unitarily invariant decomposition of Hermitian operators (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 25 (1984), S. 1045-1054 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The unitarily invariant decomposition of Hermitian operators for a boson system is performed by means of the symmetry of group SO(2, 1) and the decomposition is also closely related with Lie algebra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560250609
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  • 92
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    Theory and computational methods for studies of nonlinear phenomena in laser spectroscopy. II. Calculations of steady-state wave functions (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 51-68 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methods will be developed for variational calculations of steady-state wave functions and the corresponding quasienergies. These functions appear as solutions to the time-dependent Schrödinger equation for a molecule interacting with an oscillating electromagnetic field. A variation principle is used to obtain coupled equations for each Fourier component (FC) of the steady-state wave function. The FCs are expanded in configuration state functions using the structure of the complete active space (CAS) SCF approach. Two methods are outlined, one which is based on a common set of molecular orbitals for all FCs and one based on an individual optimization of both CI coefficients and molecular orbitals for each FC. The latter method leads to molecular orbital sets for the different FCs which are mutually nonorthogonal. Formulas are derived for the calculation of higher-order dynamic susceptibilities for steady states. An application is made to the H2 molecule, and results are presented for the frequency-dependent polarizability and hyperpolarizability along the molecular axis. The static values obtained are α = 6.413 (6.387) and γ = 676 (674) atomic units, with exact numbers within parentheses.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560260105
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  • 93
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    Ab initio calculations of guanidinium-carboxylate interaction (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 91-99 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio calculations (self-consistent-field Hartree-Fock) using 6-31G and STO-4G basis sets are used to investigate the interaction between guanidinium and methylguanidinium ion with the carboxylate group of formate. Binding energies and optimum geometries are obtained and compared with reported results using a smaller basis set (STO-3G). The importance of this interaction in proteinsubstrate binding is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560260107
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  • 94
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    Symmetry properties of chemical graphs. VI. Isomerizations of octahedral complexes (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 69-89 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Isomerization of octahedral complexes XY6, by a mechanism known as diagonal twist (in which two ligands in cis positions, one to another, exchange sites) is considered. Construction of the corresponding isomerization graph is outlined (reported before by Balaban) and the problem of determining its symmetry is considered. Alternative routes for deducing the order of the automorphism group are described. The group is confirmed to be S6 and representative symmetry permutations (one for each of the 11 classes of S6) are shown. Alternative pictorial representations of the 15-vertex graph are also shown.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560260106
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  • 95
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    A unitary group formulation of many-body theory: The spin-shift formalism (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 101-123 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper lays the algebraic foundation of a unitary group approach to many-body theory. We define a set of second quantized spin-shift operators which are used to construct spin-adapted many-electron configuration functions. We investigate the particle-hole transformation, normal ordering, and contraction of spin shifts. This gives an orbital Wick's theorem reflecting the permutational structure of the states spanning the irreducible representations of the spatial unitary group. We study the spinless Hamiltonian, and the relationship between spin shifts and unitary group generators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560260108
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  • 96
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    Bond order and valence: Relations to Mulliken's population analysis (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 151-154 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560260111
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  • 97
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    Relation between total energy, electronic potential at the nucleus, and chemical potential of positive ions (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 145-149 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Simple density functional theory gives the following relation between the energy EZ, N of an ion of nuclear charge Z and N electrons, the potential V(0) created at the nucleus by the electronic cloud, and the chemical potential μ \documentclass{article}\pagestyle{empty}\begin{document}$$ E_{Z,N} = \frac{3}{7}(ZV(0) + N_\mu). $$\end{document}Using Hartree - Fock values for V(0) and μ, this equation has been tested in several isoelectronic series with 3 ≤ N ≤ 28. The importance of the term 3Nμ/7 increases as the degree of ionization increases.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560260110
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    Masthead (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560260201
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  • 99
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    A unitary group formulation of many-body theory: Diagram systematics and use of the spin shifts (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 125-143 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper shows that the spin-shift formalism developed in B. T. Pickup and A. Mukhopadhyay [Int. J. Quantum Chem. 26, 101 (1984)] supports a one-component diagrammatics which has a systematics akin to that in the spin-orbital many-body theory. The diagrams are neither Goldstone nor Yutsis type, and characterize the chain U(2R) ⊃ U(R)⊗SU(2) on which the spin-shift formalism is based. Accordingly, while the lines in such diagrams are labeled by the orbital indices, the diagram structure adequately reflects the irreducible representation of the group U(R). In this sense the paper presents a unitary group approach to the natural generalization of the usual many-body theory for the spin-adapted cases. A set of very simple rules is derived; their similarity with the corresponding rules in the ordinary many-body theory and practical utility are discussed in connection with (a) matrix elements over many-electron spin states and (b) closed- and open-shell many-body perturbation theory. A possibility of integral-driven many-body perturbation theory for open-shells is indicated. Connections of this formalism with others are also discussed.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560260109
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    Anisotropic electronic intracule densities for diatomicsResearch supported in part by the Natural Sciences and Engineering Research Council of Canada (NSERCC). (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 26 (1984), S. 157-166 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic intracule density, a three-dimensional contraction of the spinless electron pair density, is the probability density function for an interelectronic vector. A computationally efficient algorithm for the evaluation of the basic two-electron intracule integral for GTOs is presented. In order to provide an initial understanding of the topography of intracule distributions, anisotropic intracule densities for the X1Σg+ ground states of the H2 and N2 molecules are reported and analyzed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560260202
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