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  • Computational Chemistry and Molecular Modeling  (580)
  • Wiley-Blackwell  (580)
  • 1985-1989  (226)
  • 1980-1984  (354)
  • 1940-1944
  • 1985  (226)
  • 1981  (354)
  • 1943
  • 1942
Collection
Keywords
Publisher
  • Wiley-Blackwell  (580)
Years
  • 1985-1989  (226)
  • 1980-1984  (354)
  • 1940-1944
Year
  • 1
    Electronic Resource
    Electronic Resource
    Simple relationship between total molecular correlation energies and LMO sizes (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 25-31 
    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: As an alternative to the density functional approach to estimating total molecular correlation energies, the equation Ecorr=-0.06593 ∑i=1M Ri-0.3916, where Ri=〈r2〉i½ and i runs over the localized molecular orbitals was fitted to 25 STO-3G data points with a root-mean-square error of 0.025 hartree. Other more general equations were tried but no significant improvement was observed in the fit.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190104
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  • 2
    Electronic Resource
    Electronic Resource
    Quantum mechanical calculations of vibrational transition probabilities in collinear atom-triatom collisions (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 105-112 
    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: Quantum mechanical calculations have been made of vibrational transition probabilities in the collinear collision of an inert gas atom with either CO2 or OCS. The dependence of the transition probability on the relative translational energy and the reduced mass is similar to that found for atom-diatom collisions. The transition P00 → 10 (excitation of the first stretching mode) is much greater than P00 → 01 (the second stretching mode). This is largely due to the difference in frequencies but it has been shown that there is an independent mass factor responsible for this difference.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190110
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  • 3
    Electronic Resource
    Electronic Resource
    The graph center concept for polycyclic graphsDedicated of Professor Oscar E. Polansky for his enthusiastic support, participation, and promotion of chemical graph theory at the times when such an understanding is decisive. (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 61-82 
    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: While the concept of the graph center is unambiguous (and quite old) in the case of acyclic graphs, an attempt has been made recently to extend the concept to polycyclic structures using the distance matrix of a graph as the basis. In this work we continue exploring such generalizations considering in addition to the distance matrix, self-avoiding walks or paths as graph invariants of potential interest for discriminating distinctive vertex environments in a graph of polycyclic structures. A hierachy of criteria is suggested that offers a systematic approach to the vertex discrimination and eventually establishes in most cases the graph center as a single vertex, a single bond (edge), or a single group of equivalent vertices. Some applications and the significance of the concept of the graph center are presented.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190107
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  • 4
    Electronic Resource
    Electronic Resource
    Algebraic structure of fermion density matrices. I (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 251-257 
    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: In this paper we define the algebraic structure of a reduced fermion density matrix. We relate the algebraic structure to certain symmetry properties of the reduced density matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190206
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  • 5
    Electronic Resource
    Electronic Resource
    Analysis of molecular orbital wave functions in terms of valence bond functions for molecular fragments. I. Theory (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 259-269 
    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: A method of expansion of molecular orbital wave functions into valence bond (VB) functions is extended to molecular fragments. The wave function is projected onto a basis of mixed determinants, involving molecular orbitals as well as fragment atomic orbitals, and is further expressed as a linear combination of VB functions, characteristic of structural formulas of the fragment but whose remaining bonds are frozen. Structural weights for the fragment are deduced from this expression. Delocalized molecular orbitals are used as a startpoint, as they are after an ordinary SCF calculation. Wave functions of medium-sized molecules may be analyzed with reasonable storage requirements in a computer.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190207
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  • 6
    Electronic Resource
    Electronic Resource
    Generation of generalized branching diagram spin functions by Schmidt orthogonalization of spin-paired functions (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 413-426 
    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 generalized branching diagram (GBD) spin representation is defined as the method of sequentially coupling together a number of subsystem spin eigenfunctions using the general rules of angular momentum coupling. It is shown that any GBD representation may also be obtained by Schmidt orthogonalizing a set of cannonical spin-paired (SP) functions, provided the SP basis is suitably ordered. The ordering procedure used is well suited to computer implementation. This is a generalization of results known in the literature for the Yamanouchi-Kotani and for the Serber spin representations.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190305
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  • 7
    Electronic Resource
    Electronic Resource
    Molecular orbital treatment of phenylfurans and bifurans (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 383-399 
    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 molecule-in-molecule method of computation has been applied in a SCF study of the electronic absorption spectra of 2- and 3-phenylfurans and 2,2′- and 3,3′-bifurans. The computed values for the transition energies and band intensities differ for the different isomers and help one to assign the preferred conformer of the studied molecules. Computations were performed on planar as well as nonplanar conformers. The calculated parameters as well as the interaction energy suggest all-planar configuration for the studied molecules. A model potential for the sigma framework for the ortho-hydrogens is considered. The calculated steric repulsion energy is negligible compared to the π delocalization. The height of the rotational barrier was larger for 2-phenylfuran than for 3-phenylfuran, and larger for 2,2′-bifuran than for 3,3′-bifuran. This result is in accord with predictions based on the extent of “π” conjugation in these molecules.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190303
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  • 8
    Electronic Resource
    Electronic Resource
    Theoretical study of excitation energies of some CoF6n- complexes (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 451-461 
    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: Ab initio LCAO SCF MO calculations are carried out on the ground state and d-d transition states of CoF64-, CoF63-, and CoF62- complexes with a basis set of more than double-zeta quality. To obtain a better description for the excitation energy of d-d transition states, a ligand field configuration interaction calculation is performed. The calculation is improved further by taking into account the correlation energy in the central metal atom and it gives good results for the observed excitation energies. Especially, the excitation energies for the states which have the same configuration as the ground state agree with observed ones within about 1 kK. The excitation energies of several charge transfer states in the CoF62- complex are also computed at the level of SCF MO calculation and the assignments are made for the four strong bands observed in the energy region higher than the weak d-d bands.
    Additional Material: 10 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190308
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  • 9
    Electronic Resource
    Electronic Resource
    Variational treatment of the ground state of the hydrogenic atom using the trial function φ = A exp(-αrν) (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 483-484 
    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: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190311
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  • 10
    Electronic Resource
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    Algebraic structure of fermion density matrices. II (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 505-514 
    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 properties of the algebraic structure of fermion density matrices are studied. The algebraic structure of a density matrix leads to a more varied and detailed classification scheme than that offered by the usual shell structure approach. Investigation of the algebraic structure of fermion density matrices by the methods of algebraic topology leads to a classification scheme based on Betti numbers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190404
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  • 11
    Electronic Resource
    Electronic Resource
    Masthead (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981) 
    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.560200101
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  • 12
    Electronic Resource
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    Complex formation between tryptophan-containing peptides and nucleic acids: Fluorescence decay studies using synchrotron radiation (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 41-48 
    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: Synchrotron radiation has been used to determine the fluorescence decay parameters of a tryptophan-containing oligopeptide, Lys-Trp-Lys, bound to nucleic acids. All fluorescence decay curves can be fitted by a sum of two exponentials. The two lifetimes very likely correspond to two conformational states of the oligopeptide. The mean fluorescence lifetime of the peptide is not markedly affected upon binding to nucleic acids even though the fluorescence quantum yield is strongly reduced. A model is presented that accounts for the existing fluorescence data: two consecutive complexes are formed both involving electrostatic interactions. In one of the complexes the tryptophyl ring is stacked with the nucleic acid bases and its fluorescence is completely quenched. The other complex emits a fluorescence having characteristics which are similar to those of the free peptide.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560200105
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  • 13
    Electronic Resource
    Electronic Resource
    Matrix isolated clusters and microcrystals (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 1099-1103 
    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: After emphasizing the importance of absorption spectra of metal clusters, with special reference to alkali halide IR absorption, the equilibrium configurations and the binding energies of alkali halide clusters are discussed in terms of a very simple two-body interaction.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560190618
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  • 14
    Electronic Resource
    Electronic Resource
    Molecular aspects of the hydration process in a globular protein (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 1133-1135 
    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.560190622
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  • 15
    Electronic Resource
    Electronic Resource
    Specificity and molecular mechanism of abortificient action of prostaglandins (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 167-178 
    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 paper reports comparison of electrostatic charge and energy distribution on the basis of the CNDO/2 method for six forms of prostaglandins-PGF2α, PGF1β, PGE1, PGE2, PGB1, and PGA1-having diverse physiological action. The isopotential mapping done in three dimension showed that the lower value of electrostatic potential and proximity of the two low energy regions around O9 and O11 in PGE2 and PGF2α is probably responsible for their higher abortificient activity. We also compare here the variation of the long- and short-range interaction between ring-chain and chain-chain portion of different forms and compared them with the variation in their action.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560200116
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  • 16
    Electronic Resource
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    Magnesium and calcium cation-ligand interactions within the pseudopotential approach. II. Cation-GABA interactionsSupported in part by the Polish Academy of Sciences within Project PAN-09.7.1 and Conacyt PNCB-1615, México. Presented in part at the Sanibel Quantum Biology Symposium (1979) held in honor of A. Pullman and B. Pullman. (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 463-475 
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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 performed ab initio pseudopotential and CNDO calculations on γ-aminobutyric acid (GABA) and its Ca2+ and Mg2+ clathrates. We were particularly interested in the rotational barrier existing between two extreme conformers of GABA and its modification upon metal complexing. We found that the pseudopotential method predicts a coordination of the ions to GABA and that this coordination inverts the rotational barrier observed for the isolated molecule. We also looked into the adequacy of CNDO for the study of this type of coordination and found several shortcomings in its predictions. The biological implications of these findings are discussed and a hypothesis on the role of a GABA-Ca2+ complex is presented.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560190309
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  • 17
    Electronic Resource
    Electronic Resource
    Masthead (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981) 
    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.560190401
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  • 18
    Electronic Resource
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    Direct energy minimization of self-consistent electron pair by an orthogonal transformation of the basis (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 493-500 
    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: In the frame of direct minimization of MC-SCF energy by an orthogonal transformation of the basis, a new procedure for iteratively solving the orbital equations is presented, in which the orthogonal matrix is calculated by the singular value and vector decomposition of a nonsymmetric matrix. The procedure is applied to the self-consistent electron pair theory and tested on LiH molecule. Convergence rate and numerical stability are found to be satisfactory.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/qua.560190402
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  • 19
    Electronic Resource
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    Basis set generation for the SCF calculationThis work was supported in part by the Institute of Low Temperatures and Structure Research, Polish Academy of Sciences under Contract No. MR-I.9.4.3/1. (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 545-551 
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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 method for basis set generation for SCF calculations is proposed. Using SCF orbitals and orbital energies obtained in the extended basis set the Fock operator can be expressed as its spectral resolution. The sum of differences between occupied orbital energies and corresponding eigenvalues obtained by the diagonalization of this operator in the new smaller basis set is a criterion of the quality of this new set. The present method consists of the minimization of this sum by changing the parameters that determine the new basis functions. An example of the optimization of the different Gaussian basis sets for the LiH molecule is described.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/qua.560190408
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  • 20
    Electronic Resource
    Electronic Resource
    Three-body potential energy terms for methane trimers (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 637-648 
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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 SCF LCAO MO calculation on the methane-methane-methane system is presented, in order to analyze the deviation from pairwise additivity of the interaction energy. Three-body terms are shown to be remarkably similar to those of noble gas trimers both in magnitude and in their dependence on the geometrical arrangements of the three molecules.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560190415
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  • 21
    Electronic Resource
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    Information theory interpretation of the Pauli principle and Hund rule (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 673-679 
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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: Making use of different information measures, the Pauli exclusion principle and the first Hund rule were found to be related to a trend toward acquiring a maximum information content of the atoms and molecules, and more generally, for any fermion system. The bosons conversely always have a minimum (zero) information content with respect to the permutation symmetry of their wave functions. Some new interpretations of the Pauli principle are presented.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/qua.560190418
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  • 22
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    Self-Consistent APW-k · p method. I. Theory (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 681-691 
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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 first principles method based on an APW-k · p band structure calculation is derived in order to obtain the self-consistent eigenenergies, crystal potential, and electronic density. The simplicity and extensions of the method are discussed, including comparison with the results obtained by the use of the Chadi and Cohen special points technique.
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    URL: http://dx.doi.org/10.1002/qua.560190419
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  • 23
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    Erratum (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 719-720 
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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 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560190422
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  • 24
    Electronic Resource
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    Optical oscillator strengths for isoelectronic ions of nitrogen (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 729-734 
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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 analytic atomic active electron model potential adjusted to experimental single-particle energy levels is used to generate wave functions for the valence and excited states of O1+, F2+, Ne3+, Na4+, and Mg5+. Using these wave functions in conjunction with the Born approximation and the LS-coupling scheme, we calculate optical oscillator strengths for excitations from the 1s22s22p3(4S3/2) ground state. The results are compared to experimental data and other calculations. Systematic trends along the isoelectronic sequence are discussed.
    Additional Material: 6 Tab.
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    URL: http://dx.doi.org/10.1002/qua.560190503
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  • 25
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    Coupled perturbation theory within the antisymmetrized product of separated geminals (APSG) framework (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 763-769 
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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 coupled perturbation theory for the antisymmetrized product of separated geminals (APSG) approximation is derived. The variational principle for the APSG wave function in an external oscillating field is employed and a set of equations of the form analogous to the normal RPA is obtained. At this level the reduced resolvent in the form of a spectral expansion is written and it is used for the evaluation of the second-order properties.
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    URL: http://dx.doi.org/10.1002/qua.560190507
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  • 26
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    Thermal dissociation of 1,2-dioxethane. I. Charge density distribution along the reaction path and in different HF solutions (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 805-819 
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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 charge density distribution study, based on ab initio SCF-6-31G wave functions, on the optimized geometry of 1,2-dioxethane indicates its high instability which results from (i) the high ring strain, (ii) the large amount of charge contained on the nonbonded sides of the oxygen nuclei, and (iii) the weak binding character of the charge density in the O—O bond region. The redistribution of the charge density when 1,2-dioxethane undergoes change in its nuclear configuration has been discussed. This redistribution of charge along the reaction path (the dissociation of 1,2-dioxethane to formaldehyde products) shows clearly the preceding nature of the electron cloud. The characteristic features of the charge density distribution of the two Hartree-Fock solutions to which the SCF procedure converges have been analyzed and discussed.
    Additional Material: 9 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560190511
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  • 27
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    Dynamic nonlinear Jahn-Teller effect of the type E ⊗ ∊ (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 859-871 
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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: By applying the projection operator method it is shown that the complicated Hamiltonian of a E ⊗ ∊ JT system with nonlinear coupling coefficients can be written in terms of two Hamiltonians which are simple to handle and transform according to irreducible representations E, A1, and A2 of C3v point group. A variational approach is then used to calculate the ground state energy, using the Hamiltonian that transforms according to E, as an explicit function of the linear and nonlinear coupling parameters. The energies calculated in the strong coupling limit are finally compared with the corresponding previously calculated energies.
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    Multichannel quantization and the static stark effectWork supported in part by Unité d'Enseignement et de Recherche 52, Université Pierre et Marie Curie. (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 19 (1981), S. 901-906 
    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: A coupled channel formulation for the static Stark effect on the hydrogen atom is used to obtain directly the complex resonance energies through an iterative matching procedure. The formulation makes use of a complex coordinate. This solves the initialization problem in a very simple way, since the boundary conditions can be those used for bound states. A comparison is made with the results of Reinhardt and collaborators who expand the complex rotated resonance wave function in a basis of integrable functions.
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    Energy calculations on helical polypeptides: Structure of polyglycine II (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 347-356 
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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: Single chain and packing energy calculations have been made on polyglycine (threefold and fourfold helical structures) with interchain NH…O hydrogen bonds. In conformation A of polyglycine, in which the NH groups point away from the helix axis and the CO groups are nearer to the helix axis, the conformational energy is nearly the same for threefold and fourfold structures. However, the minimum energy conformation corresponds to a threefold structure of polyglycine with peptide configurations in conformation B in which the CO groups point away from the helix axis and NH groups are nearer to the helix axis. This structure is consistent with the polyglycine II x-ray diffraction data.
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    URL: http://dx.doi.org/10.1002/qua.560200206
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    Theoretical studies of photo-oxidative cleavage reactions of nitrogen-activated C—C double bonds of enamines, indoles, and tryptamines (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 393-406 
    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 ab initio MO and semiempirical multireference (MR) CI calculations were carried out to elucidate the energy differences between peroxy 1,4-diradical (DR) and 1,4-zwitterionic (ZWI) intermediates, which play crucial roles in photo-oxygenation reactions of nitrogen-activated C—C double bonds of enamines, indoles, and tryptamines. It is found that ZWI is more stable than DR in the case of electron-rich enamines. Protic solvents such as methanol are highly effective for the stabilization of ZWI by hydrogen bondings. From the present theoretical results, it is concluded that tryptophane undergoes the photooxidative cleavage reaction to give formylkynurenine under a specific condition, where polar solvents or catalysts sufficiently stabilize the ZWI state for the species.
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    Ionophores and channels (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 461-478 
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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 present state in the chemistry of peptides and proteins capable of transporting ions across biological and model membranes have been reviewed. The mechanisms of action of peptide ionophores valinomycin and enniatin and also the channel-forming peptide gramicidin-A have been discussed on the basis of spatial structure and dynamic conformational properties of the compounds. Recent progress in the studies of bacteriorhodopsin, cholinergic receptor from postsynaptic membrane, and sodium channel from the excitable nerve membrane, the integral membrane proteins acting as proton or metal ion channel formers is also discussed.
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    Effect of change of water structure on the phase transition of liposomes of dipalmitoyl phosphatidylcholine (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 495-504 
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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 role of water structure around model membrane systems (e.g., liposomes) on phase transition of the lipid dipalmitoyl phosphatidylcholine was investigated. Water structure was altered by changing pH and by addition of solutes which are known breakers and makers of water structure. The structure makers broadened the zone of transition and changed the overall phase transition profile, while the main effect of structure breakers was to cause a shift in the transition temperature. The observed variation of Chapman transition temperature and broadening of zone of transition with varying pH is discussed in terms of altered water structure around the membrane-aqueous interface. Binding studies with the dye 1-anilino-8-napthalene sulfonate showed that structure makers or breakers did not bind to the liposome surface directly. Thus the structure makers and breakers act on the membranes perhaps by altering the water structure differentially. Possible associated mechanisms of action are discussed.
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    Interaction of the mutagenic base analogs O6-methylguanine and N4-hydroxycytosine with potentially complementary bases (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 543-554 
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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: Infrared spectroscopy has been employed to study possible base pair interactions, in nonpolar media, between O6-methylguanine and uracil, cytosine and adenine; and between derivatives of N4-hydroxycytosine and adenine. The association constants of O6-methylguanine with uracil, cytosine, and adenine are well below 1M-1, whereas those for interaction of 1-methyl-N4-methoxycytosine and its 5-methyl derivative with adenine are identical, K = 14M-1. The significance of the latter finding is discussed in relation to the conformation of the exocyclic N4-methoxy group. Quantum chemical calculations, with the aid of the perturbation method, were carried out for the interaction of O6-methylguanine with uracil, cytosine, and adenine, to establish the most energetically favoured configurations for interactions of the free bases, and of the same base pairs in the B form of DNA. The role of the conformation of the exocyclic  - OCH3 group in O6-methylguanine is discussed. The relevance of both the experimental and theoretical results to mutagenesis by O6-methylguanine and N4-hydroxycytosine is examined.
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    Masthead (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981) 
    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.560200301
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    Ab initio molecular orbital calculation of fe-porphine with a double zeta basis set (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 843-859 
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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 ab initio LCAO SCF MO calculation was performed on planar Fe-porphine with a double zeta basis set consisting of 300 CGTO's. SCF wave functions of several states of Fe-porphine and its cation were obtained. The net charge of Fe is in the range of 1.39 to 1.53. The highest occupied orbital is ascertained to be a pure porphine π-MO, 1a1u. The calculated ionization potentials of the two highest occupied orbitals, 1a1u and 5a2u are 5.98 and 6.43 eV, respectively. They are in good agreement with experiments. The role of the porphine macrocycle on the oxidation of Fe is discussed in terms of gross atomic populations and with contour maps of the density difference.
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    Limiting behavior of the ratio of 〈r12-1〉 and 〈r1-1〉 in the helium sequence (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 887-889 
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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 limiting of the 〈r12-1〈/〈r1-1〈 ratio in the He sequence is critically examined at different levels of approximations leading to some interesting results.
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    Monte-Carlo simulation of water solvent with biomolecules: Serines with reaction-field correction (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 921-926 
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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: Along the lines of previous work [S. Romano and E. Clementi, Gazz. Chim. Ital. 108, 319 (1978); Int. J. Quantum Chem. 14, 839 (1978); 17, 1007 (1980)], we carried out Monte Carlo simulation on serine-water clusters (the neutral molecule and two conformers of the zwitterion) surrounded by an appropriate dielectric continuum simulating the bulk solvent. Results for clusters in vacuo and in the dielectric continuum were compared; similarities and differences could be qualitatively interpreted as produced by competition among different factors.
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    Self-Consistent APW-k · p method. II. Application to NaCl (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 933-949 
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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 self-consistent APW-k · p method is utilized to obtain the band structure of NaCl in the “muffin-tin” approximation. Qe have investigated the convergence of many intermediate results, e.g., crystalline potential, matrix elements of the momentum operator, and energy eigenvalues at the Γ point. The summation in reciprocal space, included in the definition of the matrix D of the theory, is performed by direct sum and also by a special points technique. For the convergence criteria used, the results converged after five iterations.
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    Electron impact excitation cross sections for O II (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1073-1076 
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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: Generalized oscillator strengths and integrated cross sections from threshold to 1 keV are calculated in the Born approximation for the electron impact excitation of O II.
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    Calculation of one-electron properties using limited configuration interaction techniques (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1067-1071 
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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: One-electron properties may be evaluated by configuration interaction methods using analytical differentiation of the total energy with respect to an external perturbation parameter. Dipole moments are reported using such a method for CO and H2CO. Inclusion of single substitutions does not change calculated dipole moments appreciably with this method. The differences between this method and the direct evaluation of an expectation value are discussed.
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    A new look at correlations in atomic and molecular systems. I. Application of fermion monte carlo variational methodThis work was partially supported by the Applied Mathrmatics Programme of the U.S. Department of Energy under Contract No. DE-AC02-76ER03077 and the National Science Foundation under Grant No. CHF-8010719. (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1107-1119 
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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 are engaged in research directed toward the development of compact and accurate correlation functions for many-electron systems. Our computational tool is the variational method in which the many-electron integrals are calculated by Monte Carlo using the fermion Metropolis sampling algorithm. That is, a many-fermion system is simulated by sampling the square of a correlated antisymmetric wave function. The principal advantage of the method is that interelectronic distance rij may be included directly in the wave function without adding significant computational complexity. In addition, other quantities of physical and theoretical interest such as electron correlation functions and representations of Coulomb and Fermi “holes” are very easily obtained. Preliminary results are reported for He, H2, and Li2.
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    A hybrid technique of orthonormality constrained orbital optimization in SCF calculations (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1165-1177 
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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 orthonormality constrained orbital optimization technique is operationally modified further by coupling it to a gradient biased method, namely the steepest descent procedure of McWeeny. The hybrid technique developed in this way is shown to have better convergence properties in closed and unrestricted open-shell calculations. The technique can be adapted to MCSCF procedures as well. The important role played by "orbital symmetries" in the operation of the method is analysed. Similarities and differences of the present method with the orthogonal gradient method are pointed out. Possible avenues of circumventing convergence difficulty that one may encounter in pathological cases, particularly in ab initio calculations involving extended basis set, are suggested.
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    Catecholamine interaction with anionic sites - A model study (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1225-1231 
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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: Interactions of catecholamines with acidic sites in the biophase are likely to be involved in the control of the receptors activity as well as in storage and transport mechanisms. In view of the importance of the phenomena a model study of ethanolamine-phosphate complexes was made. The electrostatic interaction energy surface was calculated in the charge density multipole expansion approximation with terms up to quadrupole. The consecutive minimal energy conformation shows the importance for the interaction with the biophase of the catechol ring steric and electronic relation to the side chain.
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    Variants of Rayleigh-Schrödinger perturbation theory - a new look (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1273-1284 
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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: Several useful “redefined zero-order Hamiltonian” variants of the Rayleigh-Schrödinger perturbation theory are derived by exploiting the freedom of choice for the orthogonality integral between zero- and first-order wavefunctions. It is found that the more common Hamiltonian repartitioning schemes follow quite naturally, as a consequence of certain consistency requirements. The strategy adopted may as well be employed to derive various newer and profitable zero-order Hamiltonians depending on the nature of the problems. This implication is strengthened by demonstrating the calculational success of one such derived scheme. Feenberg's “scale-changed” Hamiltonian approach is also reinterpreted in the present context.
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    Catalysis in chemistry and biochemistry. Theory and experiment-jerusalem symposia on quantum chemistry and biochemistry. Vol. 12. Edited by B. Pullman. Reidel, dordrecht, 1979. Prie (cloth): $85.00. ISBN 90 - 277 - 10399 - 2. (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1331-1331 
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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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    Reactive Intermediates in the Gas Phase, Generation and Monitoring. Edited by D. W. Setser. Academic, New York, 1979. (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1333-1334 
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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.560200620
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    Ab Znitio Calculations-Methods and Applications in Chemistry. By Peter CBrsky and Miroslav Urban. Lecture Notes in Chemistry No. 16. Springer-Verlag, Berlin, 1980. ISBN 3-540-10005-9 (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1334-1335 
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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.560200622
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    Direct determination of improved contraction coefficients by a least-squares approach (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 63-71 
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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 simple method is presented for the construction of contracted Gaussian basis sets with little or no energy-optimization. The contraction coefficients are fitted by a least-squares procedure to the orbital expansion coefficients of the completely decontracted basis. The method is applied to the construction of minimum basis sets of first-row atoms from (6s, 3p) uncontracted atomic basis sets, and of [6s, 4p] contracted bases from (12s, 8p) uncontracted bases of second-row atoms. The results are better than using the expansion coefficients directly and are usually comparable to fully energy-optimized bases.The method can also be used to generate balanced atomic contraction coefficients from molecular calculations. This is shown with a (7s, 3p) and a (6s, 3p) basis, both contracted to a minimum basis. The contracted basis sets are employed in several small molecules, and the results are compared with calculations done with the decontracted bases and with contracted bases where the contraction coefficients were energy optimized in the molecules.
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    Molecular orbital studies on nucleoside antibiotics V. Conformation of pyrazofurins (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 129-138 
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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: Conformational properties of pyrazofurins, which were previously designated as pyrazomycins in both β- and α-anomeric forms, have been investigated by the PCILO method. The results indicate that the most preferred conformation for β anomer is anti-gg, while that for α anomer is syn-gg when intramolecular hydrogen bonding between sugar and the base is allowed. However, in the absence such hydrogen bonding, which mimicks the situation in aqueous solution, both β and α pyrazofurins show exactly similar preference for anti-gg conformation. The biological significance of this result has been discussed. Further the β anomer is energetically more favorable than the α anomer. This result is in agreement with the experimental observations, which indicate that β pyrazofurin is more populated than a pyrazofurin in aqueous solution at room temperature.
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    The electrostatic molecular potential of tRNAPhe. V. The influence of counterion binding on the potential and the steric accessibility (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 171-183 
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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 investigation is carried out of the influence of counterions bound to yeast tRNAPhe on the electrostatic potential and steric accessibility of this macromolecule. Two types of cations are considered, the Mg2+ ions located in the crystal of tRNAPhe, with their waters of hydration, and Na+ ions, which are positioned by theoretical estimation. Possible effects of the counterions on the chemical reactivity of tRNAPhe are pointed out.
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    Hydrogen-bonding geometry and patterns in carbohydrates and amino acids (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 231-239 
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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 hydrogen-bond geometry observed by neutron diffraction of 24 carbohydrate and 32 amino acid crystal structures is analyzed and compared. Of the 100 O—H———O bonds in the carbohydrate structures, 25 were three-centered (bifurcated). This bigamous behavior is rationalized in terms of the 25% greater number of acceptor oxygens than donor hydroxyls and the need to preserve the “cooperative effect.” The predominant hydrogen bonds in the amino acids are the zwitterion type , 64 out of a total of 145. Of these, 51 are three-centered. Again the rationale appears to be an equilization of donor and acceptor functions, since each carboxylate group generally accepts between four and six hydrogen bonds.
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    An electron spin resonance investigation of amine models for the protein-methylglyoxal interaction (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 265-270 
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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 dicarbonyl methylglyoxal reacts with the lysine residues of proteins to give brown colored products with a small oxygen-dependent free radical content. Electron spin resonance (ESR) experiments employing ethylene diamine as a model for protein lysine residues are reported. The prevention of imine formation between methylglyoxal and the amine models either by pretreatment of methylglyoxal with glutathione or by methylation of the amine led to brightly colored reaction products and a much higher radical content. From an analysis of the ESR spectra it is clear that the reactions between methylglyoxal and the simple model amines developed far beyond those in the protein-methylglyoxal systems. It is proposed that this difference is accounted for by the enormous steric effects of the proteins. The relevance of the observations to the “browning” reaction in foods is briefly discussed.
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    Electrical properties of proteins as a function of hydration and NaCl content (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 307-316 
    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: Steady-state conductivity and dielectric measurements in the range of 10-5 Hz to 33 GHz are reported for bovine serum albumin and lysozyme as a function of hydration and NaCl content. The electrical properties are understandable in terms of the existence of charge carriers whose hopping-type transport process is directly influenced by the nature of the protein-water interaction. These mobile charges are considered to be protons originating from ionizable carboxylic groups.
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    Hunting of strange electronic states and structures in solids and biopolymers (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 347-357 
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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 outlined how the authors arrived at the existence problem of the intermediate states (IS) possibly appearing in bounded crystals with perfect bulk structure and of certain zig-zag states (ZZS) in almost periodic (even disordered) biopolymers. Earlier results are summarized and commented. An example is given for how to enhance the appearance probability of ISS. It is shown that within a narrow critical interval, the width of which is about the eighth of the average separation of the bulk states in the k space of the finite linear chains, any state becomes an his (almost IS), which is very similar to the IS and approaches it continuously. Estimating the effects of in-plane and in-terplane vibrations of stacked aromatic planar compounds on the delocalized π-electron structures, it is concluded that the valence modes have a strong effect on the in-plane π-electronic systems, but a very small one on the interplane π-electronic interactions. The longitudinal acoustical modes of finite polynucleotide DNA models and their root mean square amplitudes are estimated by the method of Peticolas. According to the results obtained, DNA-like and layered graphitelike systems seem to be the probable host systems of 1%. if they exist at all. The appropriateness of the recursion method is discussed to search for unusual electronic states and structures. Such studies are the first unsteady but exciting steps toward the construction of the molecular computers.
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    Ab-initio molecular orbital study of the cis/trans conformations of the peptide bond (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 117-127 
    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: Ab-initio molecular orbital (MO) calculations on the model peptide, N-methylacetamide (NMA), protonated N-methylacetamide (p-NMA), and two natural dipeptides, glyclyglycine (Gly-Gly) and alanylalanine (Ala-Ala), are reported. Calculations at the STO-3G. 3-21G. and 4-31 G levels account for the predominance of the trans conformation in globular proteins. By use of p-NMA as a model precursor, the formation of the peptide bond is studied by the methods of molecular quantum mechanics. These calculations lead to the conclusion that the trans conformation should predominate, in agreement with the crystal structural data on globular proteins. In order to reduce the amount of computer time required for what are evidently the first ab-initio MO calculations on natural dipeptides, force-field calculations have been employed to obtain the conformational potential energy maps.
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    Molecular calculations with the nonempirical ab-initioMODPOT/VRDDO/MERGE procedures. XIV. 2,6-dimethyl-N-nitroso morpholine and its α-OH isomers: Conformations and electrostatic molecular potential contour maps (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 149-160 
    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: Ab-initio MODPOT/VRDDO/MERGE SCF calculations were carried out on 2,6-dimethyl-N-nitroso morpholine and on four isomers of α-hydroxy substituted derivatives. The NNO bond angle is found to be 1135°, in agreement with that observed in dimethyl nitrosamine. The two methyl groups are found to be most stable in the equatorial position. The axial position is found to be the most stable orientation for the α-hydroxy group in both the syn and the anti isomers. This is in agreement with the observed axial orientation of straight chain alkyl substituents at the α position in N-nitroso piperidine. An investigation was made on the effects of internal rotation in the parent compound. A 90° rotation about the N—N bond raises the energy ∼.0526 a.u. or ∼33 kcal/mol. In the 90° orientation, population analysis shows a decrease of ∼0.1 e in the gross atomic population (GAP) of the nitroso oxygen and in the total overlap population for the N—N bond. There is a corresponding increase of ∼0.05 e in the GAP on the amino nitrogen. The GAP on other heavy atoms and overlap in other bonds show little effect from internal rotation of the nitroso group. Electrostatic molecular potential energy contour maps indicate differences as a function of conformation.
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    Effects of N-protonation on the electronic structure of morphine and naloxone (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 201-219 
    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 FSGO molecular fragment technique has been employed to perform ab-initio SCF-MO calculations on morphine and naloxone in the free-base and N-protonated forms. Particular features of electronic structure which have been investigated are molecular-orbital (MO) density distributions, energies and ordering, as well as the correlation of specific orbitals between different molecular species. It has been found that high-energy occupied and low-energy unoccupied MOS are centered on the aromatic moiety of both drugs, enabling the ring to act either as an electron donor or as an acceptor in a charge-transfer interaction. Comparison of corresponding MOs in the free base and the acid cation of both morphine and naloxone demonstrates that the field of the cationic head causes a dramatic downward shift in orbital energies. Thus in the N-protonated drugs the acceptor capability of the benzene ring is greatly enhanced at the expense of its suitability as a donor. Furthermore, the allyl group of naloxone becomes highly activated as an electron acceptor through N-protonation. Investigation of the molecular electrostatic potential of the free-base species has revealed preferred avenues of approach for electrophilic and nucleophilic entities. However, the N-protonated species shows no regions of attraction for electrophiles. In both the free base and the acid cation, the vicinities of the nitrogen atom and the 3-hydroxy group are found to be favorably disposed for electrostatic interactions with receptor entities possessing the proper charge or polarity. Based on the findings with regard to electronic structure, a simple model has been suggested to explain the binding of morphine and naloxone at the opioid receptor.
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    1H nuclear relaxation study of the aniline-binding site in human hemoglobin (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 257-264 
    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: Hemoglobin-catalyzed hydroxylation of aniline may be taken as a model for similar reactions catalyzed by cytochrome P-450. Using ultraviolet-difference spectroscopy and 1H nuclear relaxation techniques, the binding of aniline to hemoglobin was examined. From the magnitude of paramagnetic effects of ferric iron on aniline protons, using the correlation time determined from the magnetic field dependence of water proton relaxation rates, aniline was found to bind to methemoglobins such that the aromatic protons are 8.5 ± 0.7 Å, away from the high-spin Fe3+. A mode of binding is proposed where the aniline molecule is hydrogen bonded to the distal histidine of hemoglobin.
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    Structure of DNA oligonucleotides (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 277-285 
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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 solution conformations of two DNA octanucleotides, (GGAATTCC)·(GGAATTCC) and (AAAGCTTT)·(AAAGCTTT), have been investigated by theoretical calculations of NMR shifts. The calculations of proton chemical shifts have been made, taking into consideration the ring current effects and the atomic magnetic anisotropies of the bases. The computed shielding constants for B-DNA, alternating B-DNA, the Levitt propeller-twisted model and the Dickerson propeller-twist model (based on crystallographic data) have been compared with experimentally available shifts. For the (AAAGCTTT)·(AAAGCTTT) double helix the experimental data are available only for the exchangeable protons HN1 and HN3; thus a complete and detailed evaluation is impossible for this system. For (GGAATTCC)·(GGAATTCC) the results indicate that the A·T pairs are propeller twisted à la Levitt and Dickerson.
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    Exponential transformation of molecular orbitals. II. General formulation for UHF calculations and application to diatomics and molecular fragments (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1285-1300 
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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 exponential transformation of the molecular orbitals, that has been previously used to achieve a process with a convergence of quadratic quality in SCF closed-shell calculations [J. Chem. Phys. 72, 1452 (1980)] has been extended to UHF determinantal wave functions built from different orbitals for different spins. Explicit formulas are given for the first and second derivatives of the energy to be varied. The method is illustrated by UHF calculations for systems described as standard singlets (Li2 and F2) or triplets (NH) at the RHF approximation level, as well as for CH, CH2, CH3 molecular fragments in their valence states.
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    Chime quantiwue structural et ét éléments de spectroscopie théorique. By A. Julg. Office des publications universitaires, Alger, 1978. (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1331-1332 
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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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    Electrons and Phonom in Layered Crystal Shuctures Edited by T. J. Wietling and M. Schluter. Physics and Chemistry of Materials with Layered Structures, Volume 3 D. Reidel, Dordrecht and Boston, 1979. (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1332-1333 
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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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    Development of a flexible intra- and intermolecular empirical potential function for large molecular systems (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 1-47 
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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 development of a flexible intra- and intermolecular empirical potential function is described, which is designed for investigating the geometric structure of large molecular systems. The intramolecular components in the potential consist of harmonic bond stretching and angle bending terms, out-of-plane deformation terms, and torsional terms; intermolecular components include nonbonding, hydrogen bonding, and electrostatic terms. Bond lengths, angles, and torsional angles are predicted to within 2% of experiment, with most cases being within 1%. The suitability of the intermolecular potential was tested by crystal packing calculations; in all cases the results obtained were in excellent agreement with experiment.
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    A theoretical study of the selective alkali and alkaline-earth cation binding properties of valinomycin (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 109-116 
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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 an attempt to account for the selectivity displayed by valinomycin with respect to the binding of alkali metal cations, theoretical computations were performed of the interaction energies of this macrocyclic carrier with Na+, K+, Rb+, and Cs+. Subtracting from these interaction energies the corresponding dehydration energies of the cations yields a set of values of the energy balance, the ordering of which follows the ordering of the binding constants measured experimentally in polar solvents. The possibility of extending the procedure to the alkaline-earth cations Mg2+ and Ca2+ is examined.
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    Ab-initio calculations of charge transfer interactions involving ascorbic acid and its metabolites (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 81-93 
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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: Ascorbic acid enhances the free radical electron spin resonance signal obtained when methylamine interacts with methylglyoxal. Previous ab-initio calculations have shown that methylglyoxal and other ketoaldehydes may act as possible electron acceptors in Szent-Györgyi's theory of cancer. Ascorbic acid is also known to be involved in cancer.The ab-initio SCF method has been used to study the electronic structure of ascorbic acid and its metabolites. The bulk of the calculations involved the use of α-hydroxytetronic acid as a model for ascorbic acid, and related compounds as models for the ascorbyl radical and dehydroascorbic acid. Complete geometry optimizations by the force method were carried out for the model compounds, using an STO-3G basis set.To obtain an estimate of possible charge transfer involving these molecules, ab-initio “supermolecule” calculations were carried out using formamide and glyoxal. A large number of planar and stacked orientations were considered The anion acts as a substantial donor in many of the stacked conformations, but the charge transfer is rather small in all these systems.
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    Implications of aminoacyladenylate conformations in the prebiotic polypeptide synthesis (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 139-148 
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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: Aminoacyladenylates play a central part in both protein enzymatic and polypeptide prebiotic synthesis. Previous general studies on aminoacyladenylate conformations were extended to some aspects related to polypeptide prebiotic synthesis. Major conclusions drawn from these quantum mechanical PCILO calculations are: (1) In the presence of an ammonium group the glycylphosphate system forms a double seven-membered ring. This folded conformation possesses an important rigidity. This occurs in neutral or acidic solutions. It agrees with experimental observations showing that there is no polymerization in this case, in the absence of catalyst. Thus the catalytic part of montmorillonite clays, which can break the ring by compensation of the anionic and cationic charges, can be understood. (2) When the amine group remains in its neutral form (in basic solutions), numerous stereo structures are allowed for the glycylphosphate stem, among which a ring of weak stability. This is still in good agreement with the observation of polycondensation at high pH without catalyst. (3) The phosphate linking system is flexible enough to allow the extension of the polypeptide chain between the clay layers. This is in accordance with the mechanism proposed by Paecht-Horowitz in which the phosphate is locked on the edge of the montmorillonite sheet.
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    Manifold theory of multidimensional potential surfaces (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 185-196 
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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: Local coordinate systems are introduced into open sets of topological spaces, defined for the nuclear configuration space R of polyatomic nuclear systems. The open sets are directly related to common chemical concepts, such as chemical structure, reaction mechanism, and stability of reaction paths. A topological model of molecules and chemical reactions is a generalization of the geometrical model, and is particularly suitable to account for the nonrigid nature of chemical structures. The coordinate neighborhoods defined on R and on its submanifolds represent the extent and natural limits for partial analyses of multidimensional potential surfaces.
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    Proton transfers in hydrogen-bonded systems V. Analysis of electronic redistributions in (N2H7)+See references [1-5] for previous papers in this series. (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 221-229 
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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 transfer of the central proton between the two NH3 units of (H3NHNH3)+ is studied using the 4-31 G basis set within the ab-initio Hartree-Fock formalism. Electron density difference maps are constructed which clearly indicate electronic redistributions which accompany the half-transfer of the proton from its equilibrium position (NH—N) to the midpoint of the hydrogen bond (N—H—N). The overall loss of electronic charge from the proton-accepting molecule originates in three distinct regions of space, while a density buildup of smaller magnitude is observed in a characteristic region centered about the N nucleus. Similar regions are noted for the proton-donating molecule, although the changes are reversed in sign. A partitioning of the total density changes into contributions from the various molecular orbitals demonstrates that the a1 orbitals are associated with density shifts along the H-bond axis. Changes in the N lone pairs are attributed chiefly to the (5a1,6a1) pair and are somewhat attenuated by opposite shifts involving the (3a1. 4a1) pair. Orbitals of e symmetry lead to polarizations of the NH bonds and density shifts perpendicular to the H-bond axis.
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    NMR probes of the spatial arrangement of substrates at the active site of creatine kinase (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 247-256 
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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: To study the arrangement of substrates at the active site of creatine kinase, we have measured the paramagnetic effects of CrADP, an exchange-incrt paramagnetic analog of MgADP, on the nuclear spin lattice relaxation rates 1 /T1 of the protons of water and the protons and phosphorus nucleus of P-creatine in the presence and absence of rabbit muscle creatine kinase. Relaxivity titrations measuring the paramagnetic effect of CrADP on 1/T1 of water protons at several concentrations of the enzyme in the presence of P-creatine were used to study the binding of CrADP to the enzyme·P-creatine complex. The existence of a ternary enzyme·CrADP-P-creatine complex was confirmed by observing the paramagnetic effects of enzyme-bound CrADP on the 1 /T1 of the 31P nucleus and protons of P-creatine. From the magnitude of paramagnetic effects arising within the enzyme·CrADP·P-creatine complex, using the electron spin relaxation time estimated from the magnetic field dependence of 1 /T1 of fast exchanging water protons, a Cr3+-phosphorus distance of 6.0 Å, and Cr3+-proton distances of 11 and 12 Å, were obtained. These results imply the absence of a direct coordination of the phosphoryl group of P-creatine by the nucleotide-bound metal on creatine kinase but indicate proximity of enzyme-bound substrates and are consistent with van der Waals contact between a phosphoryl oxygen of P-creatine and the hydration sphere of the nucleotide-bound metal. Since the metal ion is coordinated to the γ-phosphoryl group of ATP on the enzyme, the overall migration of the phosphoryl group during phosphoryl transfer is ∼3 Å, toward the nucleotide-bound metal.Creatine kinase failed to catalyze phosphoryl transfer from P-creatine to CrADP as monitored by the disappearance of the 31P NMR signal of P-creatine in a solution containing CrADP, P-creatine and creatine kinase. The ability of an isomer of β,γ-bidentate CrATP to act as a partial substrate and our observation of the absence of phosphoryl transfer from P-creatine to CrADP indicate that metal ion coordination of the transferable phosphoryl group precedes phosphoryl transfer and is a requirement of the creatine kinase reaction.
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    Muscle contraction and enzymatic action: Challenges to quantum chemistry (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 20 (1981), S. 317-329 
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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 muscle contraction is generated by interactions between the proteins actin and myosin, acting together to hydrolyze a metaphosphate bond of ATP in the presence of Mg++, using the oxygen of a specific water molecule. The molecular setting for these events is described. A key feature is identified to be an attack by the water oxygen on one of the P—O—P bonds. The resulting hydrolysis liberates a phosphate group which is forcefully repelled from its original setting, perturbing metal ions and electron orbitals in the vicinity. The hypothesis is advanced that the accompanying perturbations excite an electron cloud to a hgher energy level, leading to a forceful expansion of the electron cloud. A model is presented representing the S-l head of myosin as being tilted with reference to the coordinates of the actin filament by the expansion of this cloud. This tilt represents a leverlike movement of the S-1 myosin head which is capable of powering the work of muscle contraction. Since the most important molecular participants in muscle contraction are present in all cells, the issues raised here are of very general biological significance.
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    Warped linear analytic tetrahedral scheme for brillouin zone integrations (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 97-101 
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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 provide an alternative to the biquadratic analytic scheme BIQ published earlier. This form, AMPLIN, is similar to the older linear analytic scheme, LIN. This scheme is much faster than BIQ.
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    Announcement (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 105-105 
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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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    Isoscalar factors for tetragonal, orthorhombic, monoclinic and triclinic shubnikov point groups (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 45-58 
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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 relations between isoscalar factors for corepresentations of antiunitary magnetic point groups are discussed in the case of associated corepresentations. The tables of the isoscalar factors for the single- and double-valued corepresentations of all tetragonal, orthorhombic, monoclinic, and triclinic Shubnikov point groups are given. Some peculiarities of the calculation method of the isoscalar factors for corepresentations are considered.
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    Symmetrization of operator matrix elements (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 89-96 
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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 method of Dupuis and King for generating matrix elements of a totally symmetric one-electron operator in terms of symmetry-distinct integrals only is generalized to the case of nontotally symmetric operators. For operators constructed from two-electron integrals, explicit reduction of integral processing to permutationally inequivalent symmetry-distinct integrals only is described, while for one-electron operators further reductions are derived using double coset decompositions. Finally, some computational consequences of this approach are briefly discussed.
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    Masthead (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985) 
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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.560270201
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    EOM/Propagator ionization potentials: Effect of an extended operator manifold on the predicted valence-shell ionization spectra of ethane, ethylene, and acetylene (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 145-157 
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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 orthogonalized direct diagonalization (ODD) method is used to predict the valence-shell ionization spectra for the series of hydrocarbons ethane (C2H6), ethylene (C2H4), and acetylene (C2H2) within an EOM/propagator formalism. Both (a) third-order and (b) higher-order (with h5 terms in the excitation operator manifold) calculations are presented in order to illustrate the effect of the extended operator manifold on the predicted valence-shell spectra. It is shown that the major effect of the h5 manifold is concentrated in its “occupied” part. Along with a general shifting of the main lines for outer valence ionizations to lower values (together with a slight reduction in pole strength), it is found that the effect of the h5 manifold in the inner valence region is dependent on the system being studied.
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    Anomeric effect in phosphate moieties of carbohydrates: An Ab initio study (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 181-194 
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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 MO calculations at the STO-3G level have been carried out on CH2OHOPO3-H and CH2OHOPO32-, which have been considered as model systems for the Cl-phosphate moiety of sugars. The results predict higher anomeric energy for the phosphate moiety at Cl atom of pyranosides. Also a trans arrangement of the exocyclic O - P bond is preferred rather than a gauche arrangement, thus exhibiting a reverse exo-anomeric effect. A complete potential energy map has been constructed for CH3OPO3-H, a model system for C6-phosphate moiety. It is seen that the bond angle optimization brings down the relative energies of various conformations. The effect of the phosphate group on the preferred conformation of phosphate containing polysaccharides is also discussed.
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    Calculation of internal rotation spectra of three molecules with increasing asymmetry factors (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 235-244 
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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: Internal rotation energy levels for phenol, fluoracetaldehyde, and difluoracetaldehyde are estimated with two methods: first, by means of the reduced inertia moment formula introduced by Pitzer; second, with use of an internal axis system and by taking into account the influence of the overall rotation through the inertia factor. Two methods have been used to estimate potential barriers (CNDO/2 and PCILO). Results are related to the asymmetry of the tops. Theoretical far IR spectra for the three molecules are calculated. In the case of phenol, good agreement is found with experimental data.
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    Ab initio studies of F-(H2O)n and Cl-(H2O)n clusters for n = 1, 2 (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 281-292 
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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 Hartree-Fock calculations are performed on hydrates of the F- and Cl- ions using 6-31G, 6-31G**, and 6-21G basis sets. Geometries and binding energies are obtained. An estimate of the correlation energy is provided by an MP2/6-31G (Møller-Plesset second-order perturbation) calculation. Comparisons are made between the Cl-(SO2) and the Cl-(H2O) complexes.
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    The hydrogen molecule for a two-dimensional system (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 375-379 
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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 two-dimensional (2D) energy of the hydrogen molecule is carried out by the Heitler-London method. The 2D integrals (which are more localized compared to 3D ones) are performed in the light of the 3D Slater integrals. A discussion of such 2D systems is briefly outlined for doped semiconductors.
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    Structure of the electronic energy bands of molecular crystal NMP-TCNQ (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 407-416 
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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 electronic energy band of the molecular crystal NMP-TCNQ is calculated by means of the EHMO/LCAO-MO-CO method. In the calculation, both NMP and TCNQ are treated as quasi-one-dimensional columns, respectively. The results demonstrate that (i) the positions of the electronic energy bands of a molecular crystal are determined by that of the corresponding molecular orbitals of the respective isolated molecules; (ii) the widths of energy bands are determined by the interaction between the molecular orbitals of adjacent molecules in the crystal. These facts support the conclusion which we have given in the previous articles. The relationship between the structure of energy bands of the crystal NMP-TCNQ and its electrical conductivity at room temperature is discussed and compared with the crystal TTF-TCNQ. The differences of electrical conductivities of both crystals can be explained by the formula given by Fröhlich and Sewell.
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    Electronic structures of the π-π type charge-transfer complexes of pyridine with boron trihalides (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 465-473 
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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 electronic structures of the π-π type complexes of pyridine with boron trihalides have been studied by means of IEHMO calculation. The results indicate that BX3(X = F, Cl, Br, I) tends to react with C5H5N in a planar configurations against the plane of C5H5N. The most stable configurations of complexes are at 60° of orientation angle ϕ for X = Cl, Br, I, but at 0° for X = F. A linear relationship between In Eb, the logarithm of rotation potential barriers, and the radii of halogen atoms r0 has been observed, and has been deduced from Morse potential function. In the complex, the donating properties of BX3 have an increase from X = F to I, and BF3 functions as an acceptor, but the others as donors. It has been shown that every energy level of the complex is corresponding to that of the donor or the acceptor, which we have discussed by the perturbation theory. The bonds between D and A appear essentially as π-π type but not pure.
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    Compliant fields for molecular interactions: Water dimer and formic acid dimer (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 547-557 
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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 redundancy-free internal valence compliance constants of open-chain water dimer and formic acid cyclic dimer have been determined by the combined use of the CNDO/Force method and the compliance constant formalism. The final compliant fields of these dimers have been refined with the help of experimental frequency data.
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    New concepts in bonded functions theory. I. alternative way of matrix elements evaluation (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 613-623 
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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 new method of evaluation of energy matrix elements has been derived for bonded functions of Boys and a spinless Hamiltonian. In configuration-driven CI algorithm the new approach is two to four times faster than the original Reeves' one, the relative speed depending on the case. In integral-driven CI the new approach is about 10 to 12 times faster than the equivalent approach based on the Reeves' scheme.
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    Many-Electron, multicenter integrals in superposition of correlated configurations method. I. one- and two-electron integrals (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 641-651 
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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 calculations by means of the superposition of correlated configurations method (Hylleraas-CI), that is, the combination of configuration interaction with the Hylleraas-type correlation factors, needs the effective evaluation of some nontrivial integrals. This series of papers gives the formulas for all types of integrals needed for molecular calculations when Gaussian lobe functions are used as a basis set. The formulas for two-electron integrals are given in the present paper. The preliminary results for two-electron systems are presented.
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    An extension of the pairing theorem (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 699-707 
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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 extended pairing scheme is presented which ensures the fulfillment of pairing conditions not only between the sets of occupied orbitals for spin α and for spin β, but also between their orthogonal complements, i.e., the sets of virtual orbitals for spin α and spin β, as well as between occupied orbitals for spin α and virtual orbitals for spin β and between virtual orbitals for spin α and occupied orbitals for spin β. It is shown that the extended pairing properties are suggested by some aspects of the construction of alternant molecular orbitals. The algorithm for singular value decomposition of rectangular matrices is proposed for use in practical implementations of the (extended) pairing scheme.
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    Limiting behavior of partition functions of models with quadratically dependent energy spectra and consequences regarding theoretical study of chemical reactivity (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 691-697 
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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 conventional partition functions of models with quadratically dependent energy spectra (e.g., translation in a box or free internal rotation), which are widely used in literature, exhibit an incorrect limit behavior in the region of low temperatures and/or small values of the characterizing molecular parameter. In particular, this leads to the absurd value  - ∞ for the contribution of these motions to the entropy term at these limit conditions. This incorrect behavior appears to be due to the replacement of rigorous summation by integration in conventional derivation of these partition functions. The derived improved practical formulas with the correct limit behavior indicate that it will be necessary to carry out quite substantial numerical corrections in the case of many reactivity characteristics reported in the literature. Particularly, the improved formulas should be applied with (small) molecular complexes at the typical temperatures of their observation, e.g., van der Waals molecules with free internal rotation. Simultaneously discussed is the possibility of application of the functional relation valid for a rigorous partition function of the considered type of energy spectrum. The reasoning in the case of the translational partition function indicates that, in principle, it can depend on the vessel shape. Possible consequences for thermodynamics of the ideal gas are analyzed.
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    N-Representability conditions generated by a one-particle grassmann factor of an antisymmetric function (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 709-730 
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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: N-representability conditions for a two-particle density operator implied by positive-semidefiniteness of the projection operator PN+1(φ1 Λ ΨN) are derived and discussed. The operator PN+1(φ1 Λ ΨN) projects onto an (N + 1)-particle antisymmetric function φ1 Λ ΨN, the Grassmann product of a one-particle factor φ1 and an N-particle factor ΨN. The polar subcone P2N(g, q) to the set of N-representable two-particle density operators P2N which corresponds to these conditions is found. It is shown that its extreme rays belong to two orbits for the action of the unitary group of transformations in one-particle Hilbert space. The facial structure of the convex set P2N exposed by elements of P2N(g, q) is analyzed. An example of the operator that changes the structure of its bottom eigenspace when the number of fermions N surpasses a certain value is noted. A new approach to the diagonal conditions for N-representability is found. It consists of the decomposition of the N-particle antisymmetric identity operator onto the mutually orthogonal projection operators.
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    Ab initio calculations on H transfer in the HF trimer (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 781-786 
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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: Systematic ab initio LCAO MO calculations with basis sets of increasing size have been performed to analyze the changes in relative stabilization energies of the two cyclic (D3h and C3h symmetry) and the noncyclic HF trimers. The results form the basis for a discussion of cyclic H-transfer reactions.
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    Chemical ordering of molecules: A graph theoretical approach to structure-property studies (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 1-16 
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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 problem of ordering of chemical structures and subsequent comparison of their relative properties is initiated here by an approach which uses chemical points of view as well as graph theoretical considerations. Briefly, a collection of structurally related compounds (such as isomers, but even more broadly, compounds of similar chemical architecture even if involving different atoms) is examined pairwise and the degree of structural similarity is deduced from a comparison matching of their skeletons. Depending on the nature of the similarity found, some compounds qualify as related and are depicted as vertices of a graph with the corresponding connection. The derived “comparison graph” represents the framework for subsequent comparison of selected molecular properties. “Comparison graph” can also be viewed as depicting a hierarchy of dominance for the compounds and can be drawn with arcs (directed edges), or alternatively as a poset (partially ordered set). Usefulness of such viewing on a collection of structures is illustrated on hexane and heptane isomers and their properties. The results are discussed, particularly with respect to alternative ordering schemes. It was found that the present approach complements and does not duplicate other results, thus offering some novel structural insights.
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    Maximization of atomic information-entropy sum in configuration and momentum spaces (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 311-314 
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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 maximum entropy procedure (MEP) of Jaynes has been extended to the case involving constraints in complementary spaces. It has been rigorously shown that the sum of information entropies in position and momentum spaces is invariant to uniform scaling of the electron coordinates. A new MEP procedure requires that this sum of entropies must be maximized subject to the known constraints in both spaces. A specific application of this maximization procedure for synthesizing atomic-electron densities in coordinate and momentum spaces has been outlined.
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    Molecular orbital study of the ring nitrogen basicity of various dihydrofolate reductase inhibitors (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 315-334 
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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 molecular orbital (CNDO/2) calculations on the key fragments of different dihydrofolate reductase inhibitors. Distance geometry analysis, physicochemical parameter dependent QSAR, and molecular shape analysis raised some questions regarding the basicity of the ring nitrogen (N1) in these inhibitors and the effect of the various substituents on the basicity. We show that the ring nitrogen N1 of methotrexate has a considerably higher tendency to be protonated compared to that of folic acid. However, not all 2,4-diamino inhibitors are equally basic. Even 2-amino-4-hydroxyquinazoline is sufficiently basic to be protonated, but not the 2,4-diamino-5-sulfonyl derivatives. The pyrimidinium ion seems to be highly solvated, since in spite of its high protonation energy it is strongly basic. Triazines were found to be the most basic of all the classes studied.
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    Bond order and valence: Relations to Mulliken's population analysis (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 419-419 
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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.560280309
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    Theoretical studies on the interaction of proteins with base pairs. II. Effect of external H-bond interactions on the stability of guanine-cytosine and non-Watson-Crick pairs (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 399-409 
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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 studied the stability of guanine-cytosine and non-Watson-Crick pairs in the presence of H-bond interactions with various amino acid side chains, by using ab initio MO method. The external H-bond interactions stabilize or destabilize the base pairs, depending on the type of interacting residues and the site of the interaction. The pattern of the H-bond effect on the base-pair stability is quite different than in the case of adenine-uracil pair previously reported. From the present results, together with the previous results on adenine-uracil pair, we obtain a general rule for the effect of external H-bond interactions on the stability of base pairs. The site-specific effect of the H-bond interactions can be consistently explained by the cooperative interaction between external and base-pair H bonds. We discuss the application of the present results in the following biological processes: One is the protein-induced specific melting of double-stranded DNA, which is involved in transcription process. The present results suggest that H-bond interactions of protein residues at specific site of base pairs can weaken base-pair H bonding, which would assist the opening of double-stranded DNA. The other is the control of mutation in replication process. We suggest that proteins can discriminate non-Watson-Crick pairs against Watson-Crick pairs by H-bond interactions and can either induce or suppress mutation during DNA replication.
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    Bond length alternation in cyclic polyenes. VI. Coupled cluster approach with wannier orbital basis (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 459-479 
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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 role of electron correlation effects on the bond-length alternation in linear metalliclike systems, as modeled by cyclic polyenes CNHN, N = 2n = 4v + 2, v = 1,2,…, is examined using the coupled cluster approach in the localized Wannier basis formalism. A recently developed approximate coupled pair approach which accounts for connected quadruply excited clusters is employed together with various truncation schemes for the localized doubly-excited cluster components. It is found that for the physical value of the coupling constant, the electron correlation has only a very slight effect on the potential energy curves, yielding almost the same values for both the magnitude of the bond-length alternation and for the stabilization energy relative to the symmetric equidistant structures as the restricted Hartree-Fock theory. This is in contrast to a strongly correlated region where the correlation effects stabilize the undistorted non-alternating structures. Different mechanisms of the bond-length alternation or Peierl's distortion as implied by a simple Hückel Hamiltonian and by the Pariser-Parr-Pople Hamiltonian models are also pointed out.
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    Masthead (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985) 
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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.560280501
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    The INDO/2-AHP (average hole potential) method for excited states: Comparison with the simple INDO/2-HP (hole potential) method (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 565-571 
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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 INDO/2 version of the average hole potential (AHP) model is analyzed. The model is applied to study the geometric features, molecular inversion barriers, singlet-triplet splittings, etc., of a few small carbonyl molecules (H2CO, HFCO, F2CO) in the 1,3nπ* states with partial as well as complete optimization of all geometric parameters in the excited states. The results are compared with those obtained by a simple hole-potential (HP) model.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280503
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  • 98
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    Electronic Resource
    Perturbation calculation on the hydrogen atom in electric and magnetic fields (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 603-607 
    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: A generalization of a perturbation theory without wave function is developed which applies to a hydrogen atom perturbed by magnetic and electric fields. A double perturbation expansion for the Stark-Zeeman effect for parallel fields is considered and results for the states obeying |m| = l = n - 1 in the zero field limit are presented. Other problems that can be treated this way are discussed.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280507
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  • 99
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    Electronic Resource
    Effect of some factors on the energy band structure of proteins (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 573-579 
    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 effects of four factors (different side chains, side-chain disorder, conformational change, and ions and water) on the energy band structures of proteins have been investigated with the aid of the CNDO/2 crystal orbital method. The results indicate that these factors are very important. The consequences of these effects on the semiconductive properties of proteins are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280504
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  • 100
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    Electronic Resource
    Masthead (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985) 
    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.560280601
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