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  • 1
    Electronic Resource
    Electronic Resource
    Restricted Hartree-Fock and unrestricted Hartree-Fock as reference states in many-body perturbation theory: a critical comparison of the two approaches (1991)
    Springer
    Theoretical chemistry accounts 80 (1991), S. 407-425 
    Details
    ISSN: 1432-2234
    Keywords: Many-body perturbation theory ; Hartree-Fock ; Potential surfaces ; Open-shell systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The paper deals with two topics related to the problem which reference state is better for many-body perturbation theory: restricted Hartree-Fock (RHF) or unrestricted Hartree-Fock (UHF)? The first topic concerns the potential surfaces. Several examples are presented to show shortcomings of the two approaches and a simple way is presented which seems to give a useful potential curve in the whole range of interatomic distances by a composition of RHF and UHF potential curves. The second topic concerns the many-body perturbation theory for open-shell systems in the RHF formalism. The method is critically examined and compared with the ordinary many-body perturbation theory using UHF as the reference. This examination of many-body techniques provides also some insight into the problems inherent of the SCF theory: spin contamination from higher multiplets, localization of orbitals, and self-consistency effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01117420
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  • 2
    Electronic Resource
    Electronic Resource
    MM2 study of 20-hydroxy-4,7,13,16-tetraoxa-1,10-diazabicyclo [8,8,3] heneicosane and its formation controlled by hydrogen bonding (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 11 (1990), S. 837-847 
    Details
    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 van der Waals-type parameter set has been developed for hydrogen bonding in the MM2(85) force field to reproduce the structures and binding energies of complexes (H2O)2, (CH3OH)2, H3N … H2O, H3N … HOCH3, (CH3)3N … H2O, and HCONH2 … H2O reported in the literature. The MM2(85) force field modified in this way was then applied to the title compound to explain its unexpected stability, unusual properties of its hydroxyl group, and solvent effect on the reaction mechanism in the condensation of Kryptofix 22 ® with epichlorohydrine.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540110707
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    MM2 study on the conformation of N-acetyl-L-amino acid N′-methylamides with aliphatic side chain and their Nα-methyl derivatives (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 12 (1991), S. 829-838 
    Details
    ISSN: 0192-8651
    Keywords: Computational Chemistry and Molecular Modeling ; Biochemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: ϕ - ψ maps have been calculated by the MM2(87) potential for the Nα-acetyl derivatives of Gly, Ala, Val, and Tle methylamides and their Nα-methyl substituted derivatives to interpret the 1H NMR and CD spectra of these compounds. From the critical examination of the available theoretical and experimental evidence it follows that in the series of Nα unsubstituted Ala, Val, and Tle derivatives the importance of the second lowest energy conformation (C5) is increased and that eventually it becomes the lowest energy conformation instead of C7eq. With the Nα-methyl substituted Ala and Val derivatives, the lowest energy conformation seems to be C7eq. Performance of MM2(87) was tested for the ϕ - ψ map of the Ala derivative by comparing it with other theoretical data available in the literature.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540120707
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    Paper (German National Licenses)
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