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  • Electronic Resource  (2)
  • Computational Chemistry and Molecular Modeling  (1)
  • Electron correlation  (1)
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  • Electronic Resource  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    RI-MP2: first derivatives and global consistency (1997)
    Springer
    Theoretical chemistry accounts 97 (1997), S. 331-340 
    Details
    ISSN: 1432-2234
    Keywords: Key words: Gradients ; Perturbation theory of electronic structure ; MP2 ; Electron correlation ; Coulomb interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract. The evaluation of RI-MP2 first derivatives with respect to nuclear coordinates or with respect to an external electric field is described. The prefix RI indicates the use of an approximate resolution of identity in the Hilbert space of interacting charge distributions (Coulomb metric), i.e., the use of an auxiliary basis set to approximate charge distributions. The RI technique is applied to first derivatives of the MP2 correlation energy expression while the (restricted) Hartree-Fock reference is treated in the usual way. Computational savings by a factor of 10 over conventional approaches are demonstrated in an application to porphyrin. It is shown that the RI approximation to MP2 derivatives does not entail any significant loss in accuracy. Finally, the relative energetic stabilities of a representative sample of closed-shell molecules built from first and second row elements have been investigated by the RI-MP2 approach, and thus it is tested whether such properties that refer to potential energy hypersurfaces in a more global way can be described with similar consistency to the more locally defined derivatives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002140050269
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Improvements on the direct SCF method (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 10 (1989), S. 104-111 
    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: Three improvements on the direct self-consistent field method are proposed and tested which together increase CPU-efficiency by about 50%: (i) selective storage of costly integral batches; (ii) improved integral bond for prescreening; (iii) decomposition of the current density matrix into a linear combination of previous density matrices - for which the two-electron contributions to the Fock matrix are available - and a remainder ΔD, which is minimized; construction of the current Fock matrix only requires processing of the small ΔD which enhances prescreening.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcc.540100111
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    Paper (German National Licenses)
    Fulltext
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