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  • 2020-2023
  • 1970-1974  (362)
  • Physics  (311)
  • Atomic, Molecular and Optical Physics  (51)
  • 1
    Electronic Resource
    Electronic Resource
    SCF perturbation theory and intermolecular interactions (1972)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 6 (1972), S. 555-574 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A self-consistent perturbation theory is derived in the framework of Roothaan's MOLCAO procedure for closed shell systems. Contrary to previous investigations which have considered only one particle perturbations, two particle perturbation operators are considered. Expressions for the first-order density matrix and first- and second-order energy corrections are obtained. A diagram formulation of the complete perturbation expansion is presented.The results are applied to the treatment of the intermolecular interaction problem. The interaction energy is represented as a sum of several contributions: Coulomb, exchange, resonance, polarization and exchange repulsion. A semi-empirical version of the theory is suggested which explicitly involves all the physically significant energy terms and may be useful for the investigation of complex systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560060317
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  • 2
    Electronic Resource
    Electronic Resource
    Interaction of two H2 molecules: Comparative study of various perturbation procedures (1974)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 8 (1974), S. 467-489 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A variational calculation of the interaction between two H2 molecules using minimal basis set of 1s functions is performed to check the efficiency of various versions of the perturbation theory for intermolecular interactions. The matrix procedure starting with the zero-order Hamiltonian which is symmetric with respect to intermolecular electron permutations shows better convergence than the procedures using nonsymmetric zero approximations. This conclusion follows from the calculations of ground state and four lowest excited states for three geometric configurations of the H4 system. The behaviour of the potential curves is interpreted in terms of symmetric perturbation theory. The various contributions to the interaction energy are considered in detail. The importance of charge transfer states for the description of the intermediate range of intermolecular separations is specially emphasized.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560080312
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  • 3
    Electronic Resource
    Electronic Resource
    Intermolecular interactions in the region of small overlap (1972)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 6 (1972), S. 23-45 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In order to treat the interaction energy of two molecules a standard Rayleigh-Schrödinger perturbation theory is developed. The Hartree-Fock functions of the separated molecules are used as one particle basis functions, the initial set of states being truncated and non-orthogonal. The non-orthogonality is included into the Hamiltonian by orthogonalization of the basis set. The unperturbed Hamiltonian is chosen so that it possesses the correct symmetry properties with respect to the electron permutations between different molecules. The procedure of this kind automatically results in the appearance of charge transfer states.A graphical technique is elaborated which is a modified version of the Feynman-Goldstone technique and provides a convenient representation of the interaction energy contributions of any order. As an example the first- and the second-order diagrams are considered.A correct expression for the dispersion energy is obtained which differs by a factor from that of the theory using a nonsymmetrical zero approximation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560060103
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  • 4
    Electronic Resource
    Electronic Resource
    Evidence for ionic clusters in butadiene-methacrylic acid copolymers neutralized with various salts (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 12 (1974), S. 115-130 
    Details
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Effects of neutralization on butadiene-methacrylic acid copolymers have been studied. In Hycar CTB with 2% acid groups, small-angle x-ray scattering gives evidence of some cation clustering and leads to a value of the mean radius of 5.6 Å for the clusters and a value of the distance between them of 70 Å. When the concentration of salt is increased there is no appreciable change in the distance between clusters or in their size, but their number increases. The structure of clusters has been studied by electron paramagnetic resonance in copolymers neutralized with copper salts. The appearance of a line as in the monohydrated acetate salt permits one to define the structure of clusters consisting of two Cu2+ and four RCOO- ions with two H2O or RCOOH molecules. When the temperature is increased, the signal corresponding to Cu2+-Cu2+ pairs disappears. In high molecular weight butadiene methacrylic acid copolymers with 9% acid groups, we have found the ion pair clusters gathered into larger clusters. In dynamic mechanical properties, a relaxation peak appears at 340°K. We interpret this as due to breaking and possible re-forming of dipolar associations.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.180120110
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  • 5
    Electronic Resource
    Electronic Resource
    Vinylhydroquinone. III. Copolymerization of vinylhydroquinone and vinyl monomers by tri-n-butylboraneDedicated to Professor Yoshio Iwakura on the occasion of his 60th birthday. (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 12 (1974), S. 2801-2808 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The copolymerization of vinylhydroquinone (VHQ) and vinyl monomers, e.g., methyl methacrylate (MMA), 4-vinyl-pyridine (4VP), acrylamide (AA), and vinyl acetate (VAc), by tri-n-butylborane (TBB) was investigated in cyclohexanone at 30°C under nitrogen. VHQ is assumed to copolymerize with MMA, 4VP, and AA by vinyl polymerization. The following monomer reactivity ratios were obtained (VHQ = M2): for MMA/VHQ/TBB, r1 = 0.62, r2 = 0.17; for 4VP/VHQ/TBB, r1 = 0.57, r2 = 0.05; for AA/VHQ/TBB, r1 = 0.35, r2 = 0.08. The Q and e values of VHQ were estimated on the basis of these reactivity ratios as Q = 1.4 and e = -;1.1, which are similar to those of styrene. This suggests that VHQ behaves like styrene rather than as an inhibitor in the TBB-initiated copolymerization. No homopolymerization was observed either under nitrogen or in the presence of oxygen. The reaction mechanism is discussed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.170121209
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  • 6
    Electronic Resource
    Electronic Resource
    Mechanism of vinyl chloride polymerization (1974)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 12 (1974), S. 2821-2843 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An overall mechanistic scheme for the suspension polymerization of vinyl chloride is presented. The process can be resolved into five discrete stages, each of which presents a unique environment for the interaction of the systems parameters. It is shown that the surface area of the polymer formed during the reaction is not a major factor in autoacceleration and that the increase of kinetic chain length with conversion is due to a radical dilution effect. The latter is a direct result of the difference in rates between polymerization and radical formation, the former being greater. The increase of the initial polymerization rate and the reduction of autoacceleration brought about by chain transfer agents can be explained by the lower diffusion rate and greater bulkiness of the chain transfer agent radical relative to that of the monomer radical. The chaintransfer agent CBr4 is preferentially absorbed by PVC from solution in vinyl chloride. With lauryl peroxide as initiator it is shown that the “hot spot” is the result of a build-up of initiator in the monomer caused by its exclusion from the polymer phase. Vinyl chloride was found to dissolve 0.03% PVC at ambient temperature and to have no effect on the decomposition rate of lauryl peroxide.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1974.170121211
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  • 7
    Electronic Resource
    Electronic Resource
    Radiation-induced crosslinking of cellulose with acroleinPaper presented at IUPAC meeting in Macromolecular Chemistry, Budapest, August 26, 1969. (1971)
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-1: Polymer Chemistry 9 (1971), S. 1013-1025 
    Details
    ISSN: 0449-296X
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The process of radiation-induced crosslinking of cellulose is found to be highly influenced by radiation dosage and dose as well as by the solvents used and their concentration. The best crease resistance has been obtained in cases when cellulose is crosslinked with acrolein in the vapor phase. Moreover, the process is entirely radiation-induced and practically no homopolymer is formed. Chemical analysis and investigations of infrared spectra indicate that crosslinking proceeds on vinyl as well as on aldehyde groups of acrolein.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1971.150090416
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  • 8
    Electronic Resource
    Electronic Resource
    Symmetry in the Heitler-London method. I. The connection of the molecular point group with its electron permutation group in the Heitler-London method (1974)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 8 (1974), S. 163-169 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The connection between the electron coordinates permutation group and the molecular point group is exhibited in the framework of the Heitler-London method. It is shown that the initial wave function of a molecule in the Heitler-London method can be written in such a form, that the effect of the point group operations upon this function corresponds to the permutation of the sets of electron coordinates of the ions and the subsequent multiplication of this function by some constants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560080203
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  • 9
    Electronic Resource
    Electronic Resource
    Symmetry in the Heitler-London method. II. The determination of the allowed molecular multiplets (1974)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 8 (1974), S. 171-177 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the framework of the Heitler-London method, a method for determining the allowed molecular multiplets is proposed. The method is based on the connection of the total molecular spin with the permutation symmetry of the coordinate wave function and on the isomorphism of the molecular point group with a certain subgroup of the electron permutation group. The method does not depend on the approximation in which the molecular ions are considered.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560080204
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  • 10
    Electronic Resource
    Electronic Resource
    Some developments in the spin-extended Hartree-Fock method (1973)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 7 (1973), S. 425-457 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: All the second-order density matrix spin components for the spin-extended Hartree-Fock method are obtained. The coefficients in the final formulae are only ωsM, ωsM±1, ωsM±2, where ωsM are the weights of pure states of spin s in the initial unprojected determinant with spin projection M. The eigenvalue problem for the best electron density natural orbitals in the spin-extended method is formulated. All the second-order transition density matrix spin components between pure spin basis functions built of orthogonal orbitals and distinguished by different core choice are also found. This basis may be used on CI calculations.
    Additional Material: 5 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560070303
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