ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Books
  • Articles  (313)
  • Data
  • Wiley-Blackwell  (313)
  • American Chemical Society
  • 2010-2014
  • 2005-2009
  • 1995-1999  (170)
  • 1980-1984  (143)
  • 1975-1979
  • 1925-1929
  • 2012
  • 1997  (170)
  • 1984  (87)
  • 1980  (56)
  • 1978
  • 1977
  • 1925
  • Computer Science  (313)
Collection
  • Books
  • Articles  (313)
  • Data
Years
  • 2010-2014
  • 2005-2009
  • 1995-1999  (170)
  • 1980-1984  (143)
  • 1975-1979
  • +
Year
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 129-133 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: MNDO and MINDO/3 calculations were used to study the photochemical formation, thermal rearrangements, and dissociation of bicyclo[2.1.0]pentenone. The “forbidden” thermal conversion to cyclopentadienone requires little activation, which accounts for the low kinetic stability of bicyclo[2.1.0]pentenone. The theoretical results seem to be compatible with the available experimental evidence for the tri-tert-butyl-substituted systems and suggest an explanation for observed differences in reactivity.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 134-140 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Several “core-deficient” small Gaussian basis sets were constructed and analyzed in terms of the balance requirements of functions that contribute predominantly to the core. Variations in the conformational energy barriers and geometrical parameters for ammonia and ethane, calculated with these basis sets, were analyzed with a gradient technique. A scheme for the reduction of the size of molecular basis sets is proposed.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 178-180 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Unrestricted Hartree-Fock (UHF) SCF-MO calculations on the doublet reaction surface for the addition of methylidyne (CH) to ethylene (C2H4) using the standard extrapolation techniques of the GAUSSIAN 70 program show erratic behavior. On the other hand, the potential energy surface calculated without extrapolation of the density matrix and by using the final density matrix of a neighboring point as the initial guess for the density matrix for the new point gave a smooth potential curve without any kinks or erratic pattern. Therefore, the density extrapolation technique should be used with particular caution in UHF calculations.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 181-184 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The energies of four different conformations for n-butane were calculated by the ab initio method using an STO-3G basis set. Fully relaxed molecular geometries obtained from molecular mechanics (MM2) were used. The two energy minima [anti (C2h), gauche (C2)] and the two maxima (C2, C2v) had the following relative energies: 0.0, 0.88, 3.56, 5.99 kcal/mole. These are approximate Hartree-Fock numbers. It is estimated that inclusion of electron correlation in the calculation would lower the last number to about 5.1 kcal/mole while leaving the first three values essentially unchanged.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980) 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 199-203 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Open (1) and cyclic (2) singlet forms of CO3 were investigated by means of ab initio calculations. At the highest level of theory employed, MP2/6-31G* (which includes the effects of electron correlation), 2 was indicated to be much more stable than 1 and thermodynamically stable toward dissociation into CO2 and O(3P). The open form 1 has a long O—O bond and can be regarded as a weak dative complex between CO2 and a singlet oxygen atom.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 205-228 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Four minimal Gaussian basis sets are generated for the second-row atoms Li through Ne. The first one, MINI-1, consists of a 3-term contraction of primitive Gaussian-type orbitals for 1s, 2s, and 2p atomic orbitals. The convenient shorthand notation would be (3,3) for Li—Be and (3,3/3) for B—Ne. The second one, MINI-2, can be represented by (3,3/4) for B—Ne. In the same way, MINI-3 is described as (4,3) for Li—Be, and MINI-3 and MINI-4 are represented by (4,3/3) and (4,3/4) for B—Ne, respectively. Although the four basis sets are the minimal type, they give the valence shell orbital energies which are close to those of DZ. These four and other sets derived from them are tested for the hetero- and homodiatomic molecules and some organic molecules. They are found to give the orbital energies that agree well with those given by extended calculations. Atomization energies and other spectroscopic constants are also calculated and compared with those of extended calculations. The results clearly indicate that the present basis sets can be used very effectively in the molecular calculations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 76-80 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Empirical force field calculations were performed on hexamethylbenzene to elucidate the internal motions of the methyl groups. When the benzene ring is constrained to be planar (as in solid-phase studies), the methyl groups undergo a geared, disrotatory motion. When this constraint is relaxed, results are force field dependent. Calculated barriers are in good agreement with experimentally determined values.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 88-93 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The total energies and one-electron energies for first- and second-row atoms were calculated by using the Hartree-Fock and the Hartree-Fock-Slater Hamiltonian with Xα orbitals, ui(αexp); α was parametrized from EHFS(αexp) = Eexp. The EHF(αexp) total energies are always higher than the Hartree-Fock energies for the atoms. The relation of the calculated ionization potential to the experimental ionization potential depends on the α used to define ui(α), αexp, or αHF.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980) 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 11
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 111-117 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A molecular mechanical force field for fluorinated ethylenes and propylenes is described. The field computes geometries, dipole moments, and energy differences between isomers and rotamers. Component analysis indicates that “classical” strains alone (skeletal, nonbonded, electrostatic) cannot account for energy relationships. The discussion is supplemented by a semiempirical quantum chemical comparison of cis- and trans-FCH=CHF and of gauche- and anti-FCH2CH2F.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 12
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio molecular orbital calculations have been carried out for the neutrals X—NH2, X—OH, and X—F and the anions X—NH- and X—O- with substituents X = Li, BeH, BH2, CH3, NH2, OH, and F. All structures have been fully optimized with the 4-31G basis set which is found to perform considerably better than the minimal STO-3G basis in predicting the lengths of strongly polar bonds. A quantitative analysis of interactions between the directly bonded groups, utilizing energy changes in hydrogenation reactions, is presented and rationalized with the aid of perturbation molecular orbital theory. Favorable interactions occur when electron-donor groups bond to electron-acceptor groups. This applies to both σ and π interactions, the relative importance of which depends on the particular substituents.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 13
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 141-148 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A conformational study was carried out on the three ring-opened structures of triplet methyloxirane with a minimal Gaussian basis set, within the unrestricted Hartree-Fock framework. For the two structures energy surfaces E(θ1, θ2) were generated, where θ1 measures the methyl rotation and θ2 is associated with the torsion about the other C—C bond. For the third structure an energy hypersurface E(θ1, θ2, θ3) was generated, where energy was a function of methyl rotation θ1 and two nonequivalent C—O rotations θ2 and θ3. Analysis of the surfaces revealed the locations and relative energies of the critical points (minima, saddle points, and maxima). The overall stereochemical finding was that these ring-opened triplet C3H6O species possessed rather flexible structures.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 14
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 158-166 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The transition states for fragmentation of dihydroxycarbene [C(OH)2] to H2 and CO2 and for the rearrangement of this carbene to formic acid were located by ab initio calculations. The relative energies of the transition states were determined at several levels of theory and the basis set dependence of the energies is discussed. At the best level of theory; using a basis set of double-zeta quality augmented by polarization functions and with the inclusion of extensive CI, we found that the transition state for fragmentation was considerably higher in energy than that for rearrangement. This finding is at variance with the predictions of the Woodward--Hoffmann rules because fragmentation represents an “allowed” reaction, whereas rearrangement is “forbidden.” In conformity with the Woodward-Hoffman rules, the transition state for rearrangement was found to be close in energy to H· + ·CO2H. The even higher energy of the transition state for concerted fragmentation to H2 and CO2 is attributed to the need for the latter fragment to remain substantially bent in order to permit H2 formation while maintaining a modicum of OH bonding. Difficulties in locating the transition state for concerted fragmentation are discussed and a new method for finding transition states is proposed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 15
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio crystal orbital calculations have been performed on regular polyethylene chains applying basis sets of minimal and double-zeta quality. Relative stabilities of periodic all-trans, all-gauche, and alternating trans-gauche conformers have been evaluated, including extensive geometry optimization. Potential curves for a simultaneous rotation around C—C single bonds from the all-trans to the all-gauche conformation have been computed applying the rigid-rotor approximation, the flexible-rotor approximation, and an additional reoptimization of C—C distances. A rigid-rotor potential curve from the all-trans to the alternating trans-gauche conformation has been computed as well. Results obtained are compared with ab initio calculations on butane and pentane and with semiempirical and empirical force-field studies on polyethylene.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 16
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 64-71 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The degrees of conformational freedom of poly L-D β-helical chain are analyzed consistent with the helical parameters of gramicidin A structure. From conformational energy calculations, “helical librations” that can be sustained by this structure are described and the energy of libration as a function of the cavity size is presented. Two different modes of conformational change are identified corresponding to librations of all L-D-peptide units or all D-L-peptide units while retaining the helical parameters. Such helical librations are considered relative to conformational perturbations due to the presence of an ion in the channel.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 17
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 84-88 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The use of symmetry coordinates (SC) in geometry optimization is discussed. A computer program incorporating the use of sc, together with analytical calculation of the gradient and quadratic acceleration, is described. Also reported are careful test results on a series of small molecules and typical results with a long series of molecules up to quite large size (40-60 atoms).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 18
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 89-103 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A technique to generate electrostatic contours on a steric surface is presented and applied to the presentation of molecules that interact with DNA. A set of electrostatic points at predetermined values along with their derivatives are obtained on the steric contours as they are generated. The steric contours are generated in a set of parallel planes. Points with given electrostatic values are then connected between and within the contours mathematically with a Taylor's expansion and two rules: the first to tentatively line up points that can be connected, and the second to check to insure that the remaining points can be connected. This method insures that contours will not cross by requiring that a possible connection of two points leaves an even number of remaining points for each electrostatic value in isolated regions of unused points bounded by points that have already been connected. The hidden line algorithm used previously to draw molecules in a space-filling model within the context of steric contours is applied to the complete problem of the presentation of a molecule bound to DNA with steric contours in parallel planes, and with electrostatic contours drawn on this steric surface.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 19
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 115-121 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Analysis of a Gaussian potential function suitable for modeling degenerate bending vibrations in weakly bound molecular complexes is presented. Approximate eigenvalues and eigenvectors are obtained by application of perturbation theory. Comparison to the “exact” eigenvalues obtained via a numerical solution shows that the first- and higher-order perturbation corrections are consistent with variational principles.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 20
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 170-174 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: An algorithm is described for generating atomic Cartesian coordinates of conformations of macrocyclic molecules possessing exact rotational or rotation-reflection symmetries. A fragment representing the asymmetric unit of the molecule is suitably oriented in space, and then a symmetry operator is applied to generate the initial coordinates of the molecule. An empirical force field of interatomic interactions is used to generate equilibrium conformations. Results of calculations performed on two cyclic polylactones and one crown ether using this approach are given. They reveal that symmetric conformations of these molecules are often preferred. Since the latter conformations are probably responsible for the specialized properties of these molecules, this method should facilitate doing theoretical studies on these kinds of compounds.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 21
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 182-185 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The principles of a new method, the method of zero determinants, are described which can be used for the determination of the number of exponentials in accurate, multiexponential decay curves, as well as for the smoothing of multiexponential experimental data. It is based on the idea that the determinant of an overdetermined data matrix for accurate data is zero. The method is not limited by mathematical approximations, and thus uncovers the decay curve hidden in the data set.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 22
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 197-199 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Group equivalents which are useful for converting energies derived from ab initio calculations into enthalpies of formation have been obtained. They allow ΔHf to be estimated from 6-31G* energies with an uncertainty on the order of ±2 kcal/mol.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 23
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 207-215 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The effect of different exponents, Slater, Burns, Clementi, and Best Limited Molecular Orbital (BLMO) on the approximate one-electron property expectation values from minimum basis-set calculations is reported for Roothaan-Hartree-Fock (RHF), neglect of diatomic differential overlap (NDDO), and maximum overlap method (MOM) calculations on FH, CO, and LiH.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 24
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 225-229 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Changes of electronic charge distribution following the lowest singlet n-π* transitions of benzaldehyde, benzamide, benzoic acid, the phthalaldehydes, pyridine, and the diazines have been examined using the CNDO-S/CI method. A Singlet n-π* transition is found as a general rule to direct electronic charges to the para position of the atom in the ring that carries the lone pair or to which the substituent carrying the lone pair is attached.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 25
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 261-262 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 26
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 241-247 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Previous investigators have shown that statistical mechanical averages for configuration-dependent physical properties of long unperturbed polyoxyethylene chains are sensitive to the gauche-trans energy difference for rotation about C—C bonds. Agreement between theory and experiment could be obtained only by significant adjustment of this energy away from values predicted by semiempirical conformational energy computations. The present work examines the success of MM2 in evaluating conformational properties of long unperturbed polyoxyethylene chains. Calculations are performed which identify the rotational isomers, and their energies, for the indicated bonds in CH3OCH2CH2O—CH2—CH2—OCH2CH2OCH3. These energies are used to assign statistical weights utilized in the configuration partition function for a rotational isomeric state chain with symmetric threefold interdependent rotations. The customary generator matrix scheme is employed to evaluate the mean-square unperturbed end-to-end distance, mean-square unperturbed dipole moment, and their temperature coefficients. Contrary to computational schemes employed previously, MM2 is found to provide an estimate of the gauche-trans energy difference for rotation about C—C which is in harmony with the known dimensions and dipole moments of the unperturbed polymer. MM2 also provides good estimates for most of the other parameters required in the rotational isomeric state treatment. A notable exception is provided by the gauche-trans energy difference for rotation about the C—O bond. This energy difference is overestimated by MM2.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 27
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 272-279 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Various algorithms for evaluating nonbonded interactions in molecular dynamics (MD) simulations of macromolecular systems are considered, and a combination of two techniques using a space grid for finding neighbor atoms is proposed. The application of grid search techniques to nonrectangular periodic systems is discussed. Finally, the computing time required by different algorithms is compared on a Cray-1 vector processing computer as well as on a CDC Cyber 170/760 sequential computer. Neighbor list techniques turn out to be faster than the grid search techniques for the systems considered here. However, storage requirements may exclude the use of neighbor list techniques for large systems. Finally, MD of complex macromolecular systems turned out to be about 4-14 times faster on a Cray-1 than on a Cyber 170/760.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 28
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 280-287 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A computer program is described which evaluates the second-order Møller-Plesset energy using the integral list formed by HONDO 5. In this program use may be made of full molecular symmetry for most common point groups, even if they contain two-dimensional representations. The algorithm for the integral transformation may also be applied to other methods beyond Hartree-Fock. Some numerical results and timings are presented.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 29
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 571-575 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Classical conformational analysis was applied to the study of the variation of heats of formation (HOF) and geometrical parameters of small-ring propellanes. As expected, the calculated HOF is the smallest for [4,4,4] propellane I and the largest for [2,2,2]propellane X. In spite of the different trends exhibited by the strain energy components, the calculated HOF values may be reproduced within a simple additivity scheme. The calculated bridgehead-bridgehead bond length is the longest for [2,2,2]propellane (1.655 Å), lowers with increasing molecular size, and is equal to 1.558 Å for [4,4,4]propellane. In agreement with experimental findings the latter value is significantly larger than the standard value of 1.54 Å typical for unstrained hydrocarbons. Other calculated geometrical parameters as well as HOF values cannot be compared with experimental and/or theoretical results since there is a lack of reliable experimental data. Surprisingly, [2,2,2]propellane was found to be more flexible than the less strained bicyclo[2,2,2]octane.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 30
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 581-588 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Three newly defined information theoretic topological indices, namely “degree complexity (Id),” “graph vertex complexity (HV),” and “graph distance complexity (HD)” along with three other information indices have been used to study their discriminating power of 45 trees and 19 monocyclic graphs. It is found that the newly defined indices have satisfactory discriminating power while HD has been found to be the only index to discriminate all the graphs studied.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 31
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 589-597 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The formula for the first derivative of the MCSCF energy with respect to a nuclear coordinate is reviewed. The efficient utilization of symmetry in programs employing symmetry-adapted basis functions is described: Advantages that are also obtained for higher derivatives and for gradients of nonself-consistent wave functions are briefly discussed. Using CASSCF wave functions, the method is applied to the question of nonlinearity in the heavy atom chain of propadienone (CH2CCO).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 32
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 606-611 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The transition states involved in the hetero-Diels-Alder reactions of acrylaldehyde-ethylene and butadiene-formaldehyde systems were characterized using an efficient method of locating a saddle point on the energy surface of two coordinates calculated with MINDO/3 method. It has been shown that parallel transition and rotation of the conjugate coordinate frame lead to the reaction and orthogonal coordinate system on the hyperbolic paraboloid energy surface. It was concluded that the method we adopted is similar to the “X-method” but is much simpler to apply to real reaction systems.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 33
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980) 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 34
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Orbital mapping analysis, based on EHT and CNDO/2 semiempirical molecular orbitals, has been used to survey the thermal, disrotatory, ring-opening isomerizations of bicyclo[2.2.0]hexa-2,5-dienes (Dewar benzenes), bicyclo[2.1.0]pent-2-enes, and bicyclo[2.1.0]pent-2-en-5-yl ions to their planar isomers. Results indicate that isoelectronic substitution (CH replaced by C-, O+, N, NH+, etc.) in the molecular framework may favor allowed thermal reactions in some cases, in contrast to the disallowed reaction predicted for the parent hydrocarbons.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 35
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 59-63 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Previous attempts to determine the strengths of multiple metal-metal bonds are reviewed. Estimates of 73 and 97 kcal/mole for the Mo—Mo bond energies in Mo2Cl84- and Mo2(O2CH)4, respectively, are obtained by combining the known experimental bond energy in Mo2 (96.5 ± 5 kcal/mole) with the results of SCF-Xα-SW calculations on Mo2, Mo2Cl84-, and Mo2(O2CH)4. Possible errors in the estimates are discussed. It is noted that the quadruple bonds in the complexes are predicted stronger per component than the sextuple bond in the diatomic.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 36
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 64-68 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A recently developed ab initio pseudopotential molecular orbital approach was applied to the Te42+ ion, a system outside the practical reach of conventional all-electron treatments. Computations were carried out with a minimal STO-4G basis set. Results account reasonably well for the observed optical absorption spectrum and suggest the origin of a hitherto unassigned weak band. Ground-state properties, which included the structure, force field, and vibrational frequencies, were also investigated. Treated as a free, gas-phase ion, tetratellurium (II) yielded a bond length 0.05 Å shorter than the experimental value for the ion in a crystal lattice. Placement of static, point-charge counterions in the Te42+ coordination sphere increased the bond length to a value 0.005 Å longer than derived by experiment. Calculations on neutral, cyclic Te4 provided a theoretical single-bond reference length 0.09 Å longer than that obtained for the ion in a counterion environment. Comparisons between observed and calculated frequencies suggest an assignment of the vibrational spectrum different from the provisional assignment in the literature.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 37
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 81-87 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The electron projection function P(x, z) = ∫ ρ(x, y, z) dy is used to evaluate charge transfer and covalency in two series of molecules, LiX and CH3X (X = Li, BeH, BH2, CH3, NH2, OH, and F), with wavefunctions derived from STO-3G, 4-31G, and, in some cases, 6-31* ab initio calculations. The precision of the method and comparison with Mulliken populations analysis are described. Particular attention is given to CH3Li which by our criteria is wholly ionic.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 38
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 94-98 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Ab initio molecular orbital calculations have been used to determine the structure of protonated ozone. Four stable minima were found on the O3H+ singlet potential energy surface. Three forms correspond to ozone protonated at the central oxygen (C2v) or at the terminal oxygen (two Cs isomers, E and Z). The fourth isomer (Cs) is a derivative of trioxirane. The most stable structure is the planar E form I. The proton affinity of ozone (to give I) is given as 123.6 kcal/mole (MP2/6-31G*//4-31G). The energy difference between I and protonated trioxirane VI is greater than that between ozone and trioxirane.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 39
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 99-109 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A study is reported of the accuracy with which the geometries of pyranose and methyl pyranoside molecules are predicted by molecular mechanics. Calculations of the conformational energies of the model compounds dihydroxymethane, methoxymethanol, and dimethoxymethane, made with the program MMI, produced results that compare well with previous ab initio molecular orbital calculations. This indicates that MMI gives a satisfactory account of the energetic and conformational aspects of the anomeric effect, a conclusion further supported by calculations on 2-methoxytetrahydropyran. The prediction of the observed preferred conformations of the primary alcohol group in aldohexopyranoses appears to be less satisfactory. MMI-CARB, a version of MMI with changes in some of the equilibrium C—O bond lengths of the program, has been used to calculate the geometries of 13 pyranose and methyl pyranoside molecules, the crystal structures of which have been studied by neutron diffraction. When the C—C—O—H torsion angles are constrained to approximately the values observed in the crystal structures, good agreement is obtained between the theoretical and experimental molecular geometries. The rms deviation for C—C and C—O bonds, excluding those significantly affected by thermal motion in the crystal structure determinations, is 0.005 Å. Corresponding figures for the valence angles that do not involve hydrogen atoms and for the ring torsion angles are 1.2° and 2.0°, respectively. The Cremer and Pople puckering parameters for the pyranose rings are reproduced within 0.026 Å in Q and 5.4° in θ.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 40
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: An algorithm is developed for generating and characterizing carcinogenic catacondensed benzenoid hydrocarbons. The bay regions in these structures are identified by a technique that we developed at Johns Hopkins. Using the three-digit code proposed by Balaban, and the concept of ring adjacency matrix expounded here, we generate catacondensed benzenoid hydrocarbons in the computer and identify the number of potentially carcinogenic bay regions in each of them. The results of computer generation agree with the combinatorial enumeration of Harary and Read. All structures containing up to five rings and some with six rings and the number of bay regions in these are presented. Computer results for the structures and bay regions of all seven-, eight-, and nine-membered unbranched catacondensed benzenoid hydrocarbons and the number of bays are available from the authors.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 41
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 30-35 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A number of cyclobutane derivatives containing one or more double bonds in endo- or exocyclic positions have been studied by the molecular mechanics method within the context of the MM2 force field. Generally speaking, the structures and energies of these compounds are well calculated in cases in which they are known experimentally and are predicted in others. Examples are shown of the use of the moments of inertia of molecules, which are known from microwave studies, in conjunction with molecular mechanics calculations to yield better structures than could be obtained by either method alone. Compounds examined include cyclobutene, methylenecyclobutane, Dewar benzene, and related compounds.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 42
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 36-45 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The variable-size simplex optimization method is used to reparametrize the I + A and β parameters of an INDO approximation to the perturbed Hartree-Fock calculation of 13C chemical shifts in hydrocarbons. The absolute shifts for 39 nuclei in a set of molecules containing up to four carbons are reproduced within a standard error of 9.9 ppm for an unconstrained optimization and to a standard error of 10.0 ppm for an optimization constrained to yield gross atomic charges in agreement with double-zeta ab initio calculations.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 43
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A topological model which provides a unifying framework for chemical reactions and molecular structure is proposed. Such basic concepts as overlap, orthogonality, reaction continuity, reaction reversibility, and orbital correspondence are incorporated into the model in a logical fashion. A chemical reaction pathway is regarded as a function that transforms a reactant topological space into its equivalent product space. The unique character usually ascribed to reactants, products, and their wavefunctions is superfluous. The model also allows considerable approximation of the wavefunctions and the reaction pathway without affecting the overall result. A simple orbital mapping technique consistent with the model which traces the transformation of orbitals using intermolecular overlaps of the orbitals is also proposed. The suitability of a given pathway (“allowed” or “forbidden”) can be deduced explicitly without invoking symmetry (or other) rules and without resorting to detailed calculation of reaction energy surfaces. The validity of the mapping procedure has been confirmed by several thermal electrocyclic reactions: the ring-opening isomerizations of substituted cyclopropyl cations, cyclopropyl anion, cyclopropanone, cyclobutene, benzocyclobutene, Dewar benzenes, and 1,3-cyclohexadiene. Orbital mapping with EHT and CNDO/2 MOs correctly predicts the reaction stereochemistry (conrotatory or disrotatory) in every case.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 44
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 348-357 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Electron density maps for the heterocycles thiophene, furan, and pyrrole are determined from ab initio 4-31G wavefunctions. The charge distributions in these molecules are analyzed in terms of the total molecular density and difference density maps and their profiles. The atomiclike core, especially the L core of sulfur, is found to play an important role, via its polarization and interaction, in determining the extent and direction of valence density transfer from the carbon to the heteroatom. The changes in the charge distributions that occur in the immediate vicinity of the heteroatoms and the relation of density quantities to binding and antibinding characteristics are discussed. The quantum topological features of the molecular charge distributions of the three heterocycles are analyzed and discussed and the different bonding situations, e.g., ring strain, ionic and covalent binding, etc., are compared in a model-independent way.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 45
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 368-372 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Prediction of the known crystal structure of cyclic-L-Ser(O-t-Bu)-β-Ala-Gly-L-β-Asp(OMe) has been attempted by establishing the low-energy conformations of the isolated molecule by conformational analysis, and then regarding each of these as a rigid molecule, by establishing the favorable crystal packing arrangements by molecular packing analysis. The theoretical model closest to the observed structure was one of the lowest-energy solutions and was recognized as essentially correct by reference to the x-ray data. The limitations of the model follow from the fact that the side chain conformations are somewhat affected by packing interactions.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 46
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The results of ab initio “supermolecule” calculations of the charge transfer between formamide and the enol forms of methylglyoxal, ethylglyoxal, dimethylglyoxal, and propenylglyoxal are compared for several different conformations of the constituent molecules. The enols were found to be poorer electron acceptors than their respective keto isomers.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 47
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: By means of the ΔSCF and transition operator (TO) methods based on a recently developed INDO extension to the first transition metal series, the first ionization potentials of benzene - chromium tricarbonyl (I), cyclopentadienyl manganese tricarbonyl (II), the iron - tricarbonyl complexes with trimethylenemethane (III), and cyclobutadiene (IV) have been calculated and compared with experimental data. It is shown that the electronic structure of I to IV can be rationalized by Hoffmann's fragment approach in both the ground state and the cationic hole states. Within the series I - IV there are remarkable energy differences in the ground state for MOs derived from the 1a1 and 1e orbitals of the M(CO)3 fragment. The observation that only one band is associated with the ionization events from MOs predominantly localized at the metal site is traced back to large relaxation effects. In the cationic hole states the split of the M(CO)3 fragment orbitals 1a1 and 1e is minute in all four compounds.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 48
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 167-177 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The geometry, harmonic and anharmonic force fields, and fundamental vibrational frequencies of cis- and trans-thiolformic acid are studied ab initio in the 4-31G basis set. An extensive comparison is made between changes in diagonal and off-diagonal quadratic and cubic force constants and diagonal stretching quartic constants in going from the chain to the ring structure in thiolformic acid and formic acid. The changes in the force constants are indicative of a much weaker interaction in the trans conformer between S—H and O=C, compared with O-H and O=C, in keeping with the weaker hydrogenbonding property of the S—H group in general.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 49
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 185-188 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: High-quality SCF-MO calculations yield a barrier to internal rotation of 1.70 kJ mole-1 for Ge2H6. A new contraction scheme is reported for Dunning's larger Ge basis set. Geometry optimization, although carried out, is unimportant in this particular calculation. Wavefunctions and properties are reported for GeH4 and the staggered and eclipsed conformers of Ge2H6. The magnitude of the calculated barrier is more physically reasonable than those deduced from experimental data. Comparisons are made across the two series X2H6 and CH3XH3.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 50
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 189-191 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A MINDO/3 study of homoaromaticity in the 3-cyclobutenyl cation and the Mobius 3-cyclobutenyl anion has been used to evaluate cationic and anionic homoaromaticity quantitatively. π Homodelocalization energies of the two are found equal in isostructural planar comparisons. In planar optimized structures, the homodelocalization energy of the cation is slightly (about 4 kcal) greater than that of the anion, a consequence of the greater 1,3 distance in the latter. Full optimization produces a highly puckered and further stabilized cation, but engenders no change in the Mobius anion. The total stabilization of the cation relative to the anion is 13 kcal, in accord with the generalization that cationic homoaromaticity is more potent than the anionic variety. The fully optimized cation is revealed to actually have a much smaller π homodelocalization energy than the optimized anion, in contrast to the order of overall stabilities. σ-Nonclassical effects, which are stabilizing in the cation but destabilizing in the Mobius anion, provide the rationale for the above.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 51
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The energies of various conformations have been calculated by molecular mechanics for cis and trans isomers of 2,4,7,9-tetraoxabicyclo[4.4.0] decane and 3,5,8,10-tetraoxabicyclo[5.3.0]decane and their methyl derivatives. These molecules are models for reaction products from formaldehyde and the tetrols, pentitols, and hexitols. The conformational equilibria were analyzed for the cis-bicyclo [4.4.0] and cis-bicyclo[5.3.0] systems and compared with available experimental data. The thermodynamic stability of bicyclo[4.4.0] products was found to be higher than that of bicyclo[5.3.0] derivatives in the gas phase in every case studied. Discrepancies with experimental data that exist in a few cases can be ascribed to solvent effects.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 52
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984) 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 53
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 24-34 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We consider the problem of predicting the mode of binding of a small molecule to a receptor site on a protein. One plausible approach, given a rigid molecule and its geometry, is to search directly for the orientation in space that maximizes the degree of contact. The computation time required for such a naive procedure is proportional to n3m3, where n is the number of points in the site where binding can occur, and m is the number of atoms in the ligand. We give an alternative, combinatorial approach, in which only “contact-no-contact” criteria are considered. We relate this problem to the well-known combinatorial problem of finding cliques in a graph and show that we can use a solution to the clique problem not only to solve our original problem, but also the problem of avoiding energetically unfavorable matches. Our experience with this method indicates that the computation time required is proportional to nm2.8, with a lower constant of proportionality than that of the naive procedure.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 54
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 35-43 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Semiempirical molecular orbital calculations by the MNDO method are reported for sulfur rings and chains S3 through S8, for the corresponding dications, S22+ through S82+, and for S4+. The MNDO method seems quite successful in predicting the geometries of neutral catenated sulfur molecules, even the unusual bond-length alternation and extent of coplanarity in cyclo-S7. In contrast to hydrocarbon rings, for which its prediction of strain is erratic, MNDO is consistent in its calculated strain energies in small cyclosulfur rings; unfortunately all the strain energies are overestimated by 70%. As a consequence of this error, the method must be considered unreliable in its predictions of structures for the dications Sn2+, since many of these ions could potentially exist as strained bicyclic systems. In addition, MNDO appears to have difficulty handling long, partial SS σ bonds, as are found to occur in S82+. It may be for this reason that MNDO predicts, apparently incorrectly, that the open-chain isomers of Sn2+ are more stable than are any of the cyclic forms, at least for S52+ to S82+. With respect to neutral Sn molecules, however, the MNDO predictions appear more reliable than ab initio molecular orbital (MO) calculations using small basis sets without polarization functions and without configuration interaction (CI). However, MNDO apparently underestimates by about a factor of two the strength of the three-electron π bonds present in the terminal links of sulfur diradical chains.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 55
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The Floating Point Systems, Inc. Model 164 Attached Processor (FPS-164) is a high-speed, pipelined, parallel processor designed for large-scale scientific computation. Benchmark studies of operations common in quantum chemistry codes are discussed and the performance of the FPS-164 is compared with other commonly available computers. A complete system of electronic structure codes has been implemented on the FPS-164 using the Fortran-77 cross-compiler and calls to optimized vector and matrix routines. The conversion of a generalized valence bond (GVB) code illustrates the strategy adopted to adapt Fortran codes to the FPS-164. A typical production example, a large scale (GVB) and configuration interaction calculation on the vinyl radical, shows a net throughput equivalent to nearly nine VAX 11/780 computers.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 56
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 104-112 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We discuss the implementation and computational efficiency of one approach to adjusting the Hill equation of adsorption to a set of empirical data, pointing out some aspects that seem to be valid in the general case. The approach consists basically of minimizing squares of deviations of the adsorbed amounts, which are numerically computed in terms of the empirical pressures and the parameters. Hill's equation is dealt with as a prototype of nonlinear equations seldom used by chemists because none of their variables can be set free.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 57
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 113-113 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 58
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 129-145 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We present an approach for deriving net atomic charges from ab initio quantum mechanical calculations using a least squares fit of the quantum mechanically calculated electrostatic potential to that of the partial charge model. Our computational approach is similar to those presented by Momany [J. Phys. Chem., 82, 592 (1978)], Smit, Derissen, and van Duijneveldt [Mol. Phys., 37, 521 (1979)], and Cox and Williams [J. Comput. Chem., 2, 304 (1981)], but differs in the approach to choosing the positions for evaluating the potential. In this article, we present applications to the molecules H2O, CH3OH, (CH3)2O, H2CO, NH3, (CH3O)2PO2-, deoxyribose, ribose, adenine, 9-CH3 adenine, thymine, 1-CH3 thymine, guanine, 9-CH3 guanine, cytosine, 1-CH3 cytosine, uracil, and 1-CH3 uracil. We also address the question of inclusion of “lone pairs,” their location and charge.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 59
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A collection of programs which aid in the use of group theory has been developed for the Apple II. The programs automate much of the tedious algebra necessary to generate character tables and representation matrices from the properties of the operators chosen to generate the group. At the same time, the presentation of intermediate results provides a schematic guide to the procedures by which groups are constructed. The choice of generators is not limited to the reflections, rotations, and inversions, which are the familiar features of chemical group theory. Any generator representable as a permutation may be treated; thus general permutation groups and Longuet-Higgins groups may be studied. As an illustration we describe the states of beryllium borohydride, which require a form of Longuet-Higgins group theory.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 60
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The geometries of several conformations of ethyl and isopropyl formate were optimized by the ab initio gradient method on the 4-21G level. The calculations are in agreemnt with the existence of two conformers of ethyl formate of nearly equal energy. The COCC torsional angle in one is anti (180°) and in the other is gauche (about 80°). The equilibrium configuration of the isopropyl group in the formate is found to be unsymmetrical, with a COCH torsional angle of about 40°. A second minimum of torsional energy, at COCH = 180°, is 1.2 kcal/mol less stable than the unsymmetrical form. The calculations demonstrate the tranferability of internal rotational-potential parameters and of conformationally dependent geometrical trends between ethyl and isopropyl formate. There is good agreement between the calculated results and empirical potential-energy functions and rotational constants determined from microwave spectroscopy.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 61
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 200-206 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The conformational characteristics of allylamine were investigated by the ab initio STO-3G basis set. The results indicate that the molecule exists in a number of stable conformations through rotations about the CC—NH and CC—CN bonds. The TE (trans-CCNLP, LP representing lone-pair electrons, and eclipsed-CCCH) is the most stable, while TC (trans-CCNLP and cis-CCCN), GE (gauche-CCNLP and eclipsed-CCCH), G′C(gauche′-CCNLP and cis-CCCN), and G′E (gauche′-CCNLP and eclipsed-CCCH) conformations are less stable, respectively, by 0.41, 0.67, 0.92, and 1.14 kcal mol-1. These results are in general consistent with previous experimental results. Rationale for the conformational characteristics and order of stabilities are explored.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 62
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984) 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 63
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 217-224 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The MINDO/3 calculations were performed on the potential energy profile involved in the equilibrium \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} {\rm crotonic acid \rightleftharpoons isocrotonic acid \rightleftharpoons but-3-enoic acid} \\ {\rm (III)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(II)\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,(I)} \\ {\rm } \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\to {\rm propene + CO}_{\rm 2} \\ \end{array} $$\end{document}Optimized structures of stable molecules and transition states have been determined; thermodynamic stabilities of pure acids and barriers indicated that the equilibrium can be set up from any acids. It was argued that direct decarboxylation is only conceivable from (I), since in this process a 1, 5-hydrogen shift is involved, whereas a higher barrier process of 1, 3-hydrogen shift is required in direct decarboxylations from other acids. Direct interconversion of (I) and (III) was found to be unfavorable due to a high barrier involved.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 64
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 252-260 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Formulas are given for convergence-accelerated lattice sums over all intermolecular Coulomb, London, and repulsive interactions. Their implementation in the consistent force field is described. Optimum values of convergence constant and summation limit are found for r-12, r-9, and r-1 interaction terms. Energy minimization in all degrees of freedom, also intramolecular, for crystals of Ar, KCl, and C2H6 is reported.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 65
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 263-271 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The effect of correlation energy on the relative stability of different structures and dissociation products of complex lithium beryllohydrides has been investigated. The adequacy of the method employed (third-order Möller-Plesset perturbation theory) and the basis set dependence have been assessed. Trends of the correlation energy according to the molecular structure have been discussed, and the validity of an additive scheme based on electron pair contributions has been tested.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 66
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 326-335 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The tendency of C—O bond lengths to change as a function of the torsional angles at an acetal carbon has been included in a new version of the molecular mechanics program MM2(82), based on the observed behavior of molecules of this class as indicated by ab initio calculations and experimental structural data. The experimental geometries and energies are reasonably well reproduced.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 67
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We have used energy minimization calculations to study a number of conformations of uncomplexed valinomycin. In certain cases, x-ray diffraction atomic coordinates were used directly as input coordinates, while in other cases, conformations were found by altering the x-ray coordinates prior to minimization. Five calculated conformations are reported along with their relative energies. The conformation found theoretically to be the most stable is in agreement with earlier, cruder calculations, but does not correspond to the predominant conformation observed in nonpolar solvents. A possible rationale is presented.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 68
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 353-357 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The problem of determining the amount of reactant present in the steady state of a reaction-diffusion problem with pth order reaction kinetics and slab geometry can be achieved by solving the boundary value problem \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} u''(x) = \phi ^2 u^p (x),\,\,\,\,\,\,\,\,\,\,\,\,{\rm 0 〈 }x{\rm 〈 1} \\\\ u'(0) = 0{\rm }\,\,\,\,\,\,\,\,\,\,\,\,u(1) = 1 \\ \end{array} $$\end{document} where u is a normalized (dimensionless) concentration, and φ is the Thiele modulus. By considering the related nonlinear eigenvalue problem \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} y''(x) = \lambda y^p (x),\,\,\,\,\,\,\,\,\,\,\,\,{\rm 0 〈 }x{\rm 〈 1, }\,\,\,\,\,\,\,p{\rm 〈 0} \\\\ y'(0) = 0,{\rm }\,\,\,\,\,\,\,\,\,\,\,\,y(1) - y'(1) = 0 \\ \end{array} $$\end{document} and constructing a sequence of functions that converges monotonically to y(x), solutions of the original boundary value problem are obtained for the negative exponent case.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 69
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984) 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 70
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 427-440 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The force constants and compliance constants of methyl, silyl, and germyl fluoride, chloride, bromide, and iodide have been calculated by the iterative consistency method. Using the force fields so obtained, centrifugal distortion constants, Coriolis coupling constants, and mean amplitudes of vibration have been computed and compared with experimental data, where available.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 71
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The structures and conformational energies of several conformations of propanoic acid, 2-methylpropanoic acid, and butanoic acid were determined by geometrically unconstrained ab initio gradient geometry refinement on the 4-21G level. The O=C—C—C torsional potentials of propanoic acid and butanoic acid are found to be practically identical. There are energy minima at 0° and 120°, and maxima in the 60° region and at 180°. In 2-methylpropanoic acid there are energy minima at H—C—C=O dihedral angles of 0° and 120°, and maxima at 60° and 180°. The exact positions of the maxima and minima of the H—C—C=O torsional potential of 2-methylpropanoic acid are found to be predictable from propanoic acid rotational-potential parameters. Some conformationally dependent, local geometry trends are discussed.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 72
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 457-465 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A Fortran-77 computer program has been written which calculates the rotation-torsion profile of a vibronic transition using an asymmetric top/free internal rotor Hamiltonian. The program is applicable to any molecule that is composed of a frame portion of C2v symmetry a free rotor portion of C3v symmetry. Rotation-torsion bands of A-, B-, and C-type contours may be calculated within an assumed Boltzmann distribution of rotation-torsion level populations or within a specified non-Boltzmann distribution of torsional level populations.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 73
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 500-505 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The organization of a computer code to compute transition moments between states described in different orbital basis sets (a nonorthogonal transition moment) is described. The code is organized to minimize redundant work and allow efficient threshold checking. Three sample calculations are presented.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 74
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 523-527 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A numerical procedure is described and tested for the determination of solvent sites in a crystal hydrate from computer simulation results. The method does not require the computation of density distributions.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 75
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: In order to provide additional data for the relative lengths of methyl-C—H bond distances in acetyl derivatives, which are difficult to determine accurately by the conventional tools of structural chemistry, the geometries of CH3COH, CH3COF, CH3COCH3, CH3COOH, and CH3CONH2 were determined by ab initio SCF gradient optimization at the 5-31G** level and compared with previous 4-21G results. For acetaldehyde 6-311G4* calculations were also performed and the correlated methyl-C—H stretching potential energy functions were determined. It is found that the calculated differences between the in-plane and out-of-plane methyl-C—H bonds are practically independent of the computational scheme. The calculated results are in contrast to relative bond lengths obtained by some vibrational overtone spectroscopic studies, but are in perfect agreement with C—H bond length differences determined from isolated C—H stretching frequencies of partially deuterated compounds. The reliability of the latter, and other spectroscopic data concerning the assignment of the methyl-C—H vibrations are critically analyzed. On the basis of the available evidence we conclude: (1) the methyl groups of the CH3C(=O)X systems here discussed contain one strong (in-plane) and two weak (out-of-plane) C—H bonds; (2) intensities of C—H local mode spectra do not provide a reliable basis for assignment to individual bonds.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 76
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 555-561 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A generalization of the quantum chemical definition of valence of atoms in molecules is suggested. Valence is considered as expectation value of diatomic parts of density operators. It appears as a sum of contributions from occupied orbitals of all atomic pairs that contain the reference atom. This definition is applicable on self-consistent-field (SCF) and configuration interaction (CI) level in any atomic orbitals (AO) basis. Its usefulness is demonstrated in an application to special molecules. Photoelectron spectroscopy and reactivity is discussed in this context.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 77
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 299-306 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Molecular mechanical calculations for hetero-substituted hydrocarbons present certain difficulties that are not encountered in dealing with hydrocarbons. Ways are proposed to overcome such difficulties, sometimes by two-step or iterative computation. The following topics are considered: fitting the force field by using data from studies in solution; ways to estimate atomic charges or, alternatively, bond moments; ways to account for field effects upon atomic charges and bond moments.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 78
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: It is shown that a Lagrange multiplier method to constrain one or several internal coordinates, or averages and combinations of these, is easily implemented in a molecular mechanics computer program that uses Newton-Raphson (NR) minimization. Results are given for constraints on nonbonded distances and torsion angles. When a potential energy surface is to be explored, it is much better to constrain the average of three torsion angles around a bond than to constrain a single torsion angle. Certain conversions can only be achieved when averages of torsion angles around different bonds are constrained. Combinations of constraints have been applied to evaluate differences between calculated and observed geometries and to obtain transition states for relatively large molecules from results for smaller molecules at relatively low costs. The efficieny of the combination of the Lagrange multiplier method and NR minimization in terms of computing time can be rated as good.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 79
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 343-348 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Theoretical calculations by the combined empirical force-field (EFF)-extended Hückel molecular orbital (EHMO) approach confirm that octalene and benzo-|c|-octalene present π-bond fixation with a common single bond between the cyclooctatetraene and cyclooctatriene fragments, whereas the structure of dibenzo-|c, j|-octalene is characterized by a central double bond. The dynamic behavior of these compounds is discussed and the interconversion energy barriers are calculated; the inversion of the cyclooctatriene ring is faster than that of the cyclooctatetraene ring in octalene, but it is slower in benzo-|c|-octalene.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 80
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 349-352 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Formulas fully exploiting the periodicity symmetry of the electron density of polymers are deduced. They are shown to lead to efficient algorithms for the evaluation of Coulomb and exchange interactions in those systems.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 81
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 363-373 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Optimized monopole expansions for the subunits of the nucleic acids are developed by a reparametrizatio of the Hückel-Del Re procedure designed to reproduce closely the electrostatic properties obtained with precise overlap multipole expansions. It is shown that satisfactory values of both potential and field may be obtained for different DNA conformations and for a transfer RNA. The charge redistribution occuring between the subunits upon forming the nucleic acids is also investigated by ab initio calculations and accounted for in developing the new parametrization.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 82
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 381-386 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The nitrogen protonation energies of the imino bases HN=CHR, where R is H, CH3, NH2, OH, and F, have been evaluated to determine the dependence of absolute and relative protonation energies on geometry, basis set, and correlation effects. Reliable absolute protonation energies require a basis set larger than a split-valence plus polarization basis, the inclusion of correlation, and optimized geometries of at least Hartree-Fock 4-31G quality. Consistent relative protonation energies can be obtained at the Hartree-Fock level with smaller basis sets. Extending the split-valence basis set by the addition of polarization functions on all atoms decreases the computed absolute Hartree-Fock nitrogen protonation energies of the imino bases HN=CHR except when R is F, but increases the oxygen protonation energies of the carbonyl bases O=CHR.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 83
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 395-410 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The geometry and energy of 2-aza-1,3-butadiene and 2,3-diaza-1,3-butadiene have been calculated using the 6-31G* basis set as a function of the CNCC and CNNC dihedral angles, respectively. With the 2-aza derivative potential minima are located at 0° (trans) and at about 130° for a gauche structure approximately 9.5 kJ mol-1 less stable than the trans. Potential maxima are at about 75° giving a gauche barrier height of approximately 19 kJ mol-1 relative to the trans structure, and at 180° (cis) giving a barrier height of approximately 14.5 kJ mol-1 relative to the 130° gauche structure. With the 2,3-diaza derivative the gauche barrier has disappeared and there are a series of gauche structures in the region 70°-100° of almost equal energy 12.5-15 kJ mol-1 less stable than the trans. In addition the cis barrier is much greater, nearly 70 kJ mol-1 relative to the trans structure. Inclusion of electron correlation, accounting for about 50% of the correlation energy, produces no significant changes in the shape of the potential energy curves. There are systematic and progressive changes in almost all the geometrical parameters as the =CH— groups in butadiene are replaced by =N—. The outward tilt and compression within the methylene groups show adverse steric interactions to be operative in the cis structures. The values of Vnn indicate that gauche structures of both the 2-aza and the 2,3-diaza derivatives near the cis structure are more compact (as with butadiene), and gauche structures of the 2-aza derivative near the trans structure are less compact (as with butadiene). Originating in the changes in bond lengths and bond angles, rotation-independent nuclear-nuclear interactions again play an important role.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 84
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 441-450 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A number of force fields of the molecular mechanics type have been tested for their ability to represent as an energy minimum, the observed crystal structure for three cyclic hexapeptides, cyclo-(-Ala-Ala-Gly-Gly-Ala-Gly-), cyclo-(-Ala-Ala-Gly-Gly-Ala-Gly-), and cyclo-(-D-Ala-D-Ala-Gly-Gly-Gly-Gly-). The most effective force field tested was that recently proposed by Kollman and co-workers, notwithstanding its use of “united” atoms for CH, CH2, and CH3 groups. Fields proposed by Levitt, and adaptations of that of Scheraga and co-workers, were also effective. Force fields in which hydrogens bonded to electronegative atoms were not specified explicitly were less accurate in representation.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 85
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 466-470 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Structures and relative energies were obtained for the hydrogen bonded dimers of formamide and formamidic acid using the 3-21G basis set. A double proton transfer transition state is claimed to link these two dimers. While the structure of the transition state was intermediate between those of the two dimers, the energy was only 7.6 kJ/mol greater than the less stable formamidic acid dimer. The activation energy from the formamide dimer side of the reaction was found to be 125 kJ/mol of dimer. A similar transition state was found for the amidine dimer system. The activation energy for this model reaction was found to be 66.9 kJ/mol of dimer.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 86
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 486-499 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A set of procedures and guidelines are presented for the estimation of bond length, bond angle, and torsional potential constants for molecular mechanics force fields. The force field constants are ultimately derived by “subtracting” nonbonded molecular mechanics energies from corresponding molecular orbital energies using a model compound containing the chemical structure to be parameterized. Case study examples of bond length, bond angle, and torsional rotation force field parameterizations are presented. A general discussion of molecular mechanics force field parameterization strategy is included for reference and completeness. Finally, a curve-fitting program to generate force field parameters from raw data is given in Appendix I.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 87
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984) 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 88
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 528-534 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Potential energy surface for methyl fluoride dimer has been studied theoretically with ab initio molecular orbital method, using a 4-31G basis set. Dimer dissociation energies, Mulliken electronic populations, and dipole moments were obtained.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 89
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 562-570 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A previously published scheme of estimating atomic charges in haloalkanes is extended to include olefines, alcohols amines, acids, ethers, and amides. In the conjugated systems the effects of mesomeric transfer of charge are explicitly included. Generally good agreement with the observed dipole moments of these compounds and their substituted derivatives is found. The atomic charges so obtained are compared with those of other semiempirical and quantum-mechanical calculations for the amide group. The charges so obtained fall within the range of values obtained by these other schemes, supporting the general validity of this approach.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 90
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 576-580 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Accurate vibration-rotation eigenvalues EvJ are sought for very high levels (up to dissociation) of a diatomic potential. The method used is the recent “eigenvalue equation” method [Kobeissi et al., J. Comput. Chem., 4, 218 (1983)] which dissociates the determination of the eigenvalue from that of the eigenfunction. A new mathematical formulation for any numerical potential is presented, which reduces the problem to the use of a single recurrent formula. A numerical application to the model potential used by Cashion [J. Chem. Phys., 39, 1872 (1963)], up to v = 23, gives results equal to the exact eigenvalues to approximately 10-14 cm-1. Another application to the model potential used by Johnson [J. Chem. Phys., 67, 4086 (1977)], up to v = 60, gives similar results.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 91
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 535-547 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: An ab initio self-consistent-field (SCF) algorithm taking into account all the features of the one-dimensional translational periodicity and the helical symmetry is presented. This algorithm includes the long-range correction to the Coulomb potential and is designed to calculate the band structure of periodic one-dimensional polymers (planar or helical). Its efficiency in terms of computing time and numerical accuracy is tested via applications on a (LiH)n chain, polyethylene, and four conformers of polypropylene.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 92
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 1 (1980), S. 417-419 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The hydrogen-bonded complex between nitric acid and ammonia molecules has been studied by the ab initio molecular orbital method using the 4-31G basis set. The calculated interaction energy for the complex (ΔE = -91.4 kJ mole-1) indicates that one is dealing with the strongest “nonionic” H-bonded complex considered hitherto by theoretical methods. Other properties of the hydrogen-bonded complex such as geometrical parameters, dipole moment, amount of charge transfer, and stretching force constants of the O—H and (OH)… N bonds are calculated and discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 93
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 1-10 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The geometry of the ground states of the isomers and transition state for the systems HCN ⇌ HNC and BCN ⇌ BNC have been investigated using a wide variety of basis sets, both at the self-consistent-field (SCF) level and including correlation at the second-, and third-order Møller-Plesset (MP2 and MP3) levels. The barrier to isomerization and the isomerization energy were shown to be strongly dependent on the basis set and method, particularly for the BCN system.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 94
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 19-23 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The structure of an isolated, infinite polyoxymethylene chain has been investigated with the aid of the ab initio crystal orbital method applying a basis set of double-zeta quality. Restricting the primitive unit cell to a single CH2O group, conformational potential curves as a function of the torsional angle have been evaluated. Only a single minimum closely corresponding to an all-gauche structure was detected. The all-trans conformation is a maximum on the energy curve for simultaneous rotation around C—O single bonds. Detailed geometry optimization in the vicinity of the all-gauche conformation led to the following structure: rCO = rOC = 1.425 Å, rCH = 1.072 Å, ∠HCH = 111.7°, ∠OCO = 110.9°, ∠COC = 115.1°, and τOCOC = 70.75°. The computed torsional angle τOCOC lies midway between the hexagonal (78.2°) and the orthorhombic (63.5°) modification of solid polyoxymethylene.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 95
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Extension of the inhomogeneous continuum solvent model to prolate spheroidal cavity systems in the context of Kirkwood-Westheimer substituent-reactivity theory is described. Reasonable effects attributable to electrical saturation and electrostriction, which are modeled by relatively simple spatial dielectric functions outside the solute-solvent boundary, may be demonstrated. It is also shown that choices of proper (i.e., nonaveraged) location of the interacting sites and magnitude of substituent dipole moments are comparably important to the quality of theoretical prediction.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 96
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 72-83 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A simple computational scheme for estimating the electrostatic potential about molecular models of moderate size is given. The large amount of calculations required for the evaluation of the hypersurface lends itself to treatment by high speed, unconventional computing machines. The essence of these calculations lies in Coulombic interactions that are computed between hypothetical proton test probes positioned in a gridded region surrounding the model and the partial electrostatic charges (CNDO/2) of each atom in the model. A specific scientific application is discussed which involves the recognition of amino acids and nucleotide bases. Three different evaluations of the potential hypersurface within the context of this approach were made. The first was performed on a VAX 11/780 which is a general purpose machine widely used in the scientific community; the second was performed using a pipelined Vector Processor, the FPS AP-120B; and the third by a processor array, the ILLIAC-IV. A comparison of the architectures and processing speeds of each class of machines is made. The computing power observed is consistent with the design and purpose of each machine. Also discussed are methods for displaying the vast amount of data that result from such calculations. It is determined that computer graphics offers an effective means for extracting information from large amounts of data. Finally, the scientific value of the calculations are briefly discussed. If caution is applied to interpreting the results, then the electrostatic potential (EP) mappings can be useful in identifying sites of potential chemical interactions.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 97
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984) 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 98
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The geometries of several conformations of propanal and butanal have been refined by geometrically unconstrained ab initio gradient relaxation on the 4-21G level. Both compounds possess energy minima at O—C—C—C torsional angles of 0° and in the 120° region, and energy maxima in the 70° region and at 180°. The structure of the aldehyde functional group is found to be relatively invariant both when different systems or when different conformations of the same system are compared. Conformationally dependent geometrical trends in propanal and butanal are discussed and found to be subtle yet noticeable.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 99
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 146-161 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: Compact, contracted Gaussian basis sets for halogen atoms are generated and tested in ab initio molecular calculations. These basis sets have similar structure to that of Huzinaga and co-workers' (HTS) sets; however, they give both better atomic total energies and better properties of atomic valence orbitals. These sets, after splitting of valence orbitals and augmenting with polarization functions, provide molecular results that agree well with those given by extended calculations. Basis set superposition error (BSSE) is calculated using the counterpoise method. BSSE has only slight influence on calculated equilibrium geometry, shape of potential curve, and electric properties (dipole and quadrupole moments) of molecules. However, atomization energies may be significantly changed by the BSSE.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 100
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 5 (1984), S. 186-189 
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: A computational procedure, developed from the power series method, is used to investigate oscillating systems. In addition to its great accuracy and reduced computer time, the method is very easily programmable since the algorithm is provided by the reaction mechanism itself.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...