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  • 1
    Electronic Resource
    Electronic Resource
    Elastic-tensor atom–atom potential calculations for molecular crystals: C6H6 and CO(NH2)2 (1991)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 47 (1991), S. 846-850 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The numerical method for calculating the elastic constants of molecular crystals, using the crystal packing program PCK 83, developed and applied to the model case of CO2 in previous work is here extended to benzene (C6H6) and urea [(NH2)2CO] crystals. Interatomic potential-energy functions coupled with rigid-molecule constraints are used, taking the entire angular dependence into account. Correlation with other calculations and experimental data is good.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767391007353
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    On the calculation of the hyperpolarizabilities of organic molecules by the sum over virtual excited states method (1992)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 43 (1992), S. 7-26 
    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 version of time-dependent perturbation theory commonly used in the calculation of the hyperpolarizabilities of organic molecules through an expansion over electronic excited states is briefly rederived by a direct method, simplified for application to the nonresonant case. The application of the method within the framework of semiempirical quantum theory and singly and doubly excited configuration interaction is described. A particular parametrization of the CNDO/S method (CNDO/VS) that has been successful in estimating molecular β values for polar aromatic molecules is reviewed. Applications of the method to the interpretation of the molecular and crystal second-order properties of 2-(α-methylbenzylamino)-5-nitropyridine (MBANP) and to the calculation of the γ tensor for various types of conjugated compounds are given.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560430105
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Spin-Projected EHF equations (1987)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 32 (1987), S. 711-722 
    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: Extended Hartree-Fock (EHF) equations are developed for the general open-shell case using a modified pair-orthogonality-constrained variation (POCV) method. The EHF energy is expressed in terms of corresponding orbitals that are required to remain orthogonal and paired for all arbitrary infinitesimal variations.The Euler equations for each set of orbitals are reduced to unique pseudosecular equations, the LCAO form of which may easily be derived. The Euler equations and the expressions obtained for the off-diagonal elements of the ∊γδ (γ, δ = a or b) matrices for the closed-shell case are identical to those obtained by Mayer, who used the generalized Brillouin theorem method. However, the present method yields equations for both closed- and open-shell cases and for any spin state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560320609
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    Paper (German National Licenses)
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