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The effect of electron correlation on the electron density distributions of molecules: Comparison of perturbation and configuration interaction methods (1989)

Wang, Liang-Chen ; Boyd, Russell J.

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 90 (1989), S. 1083-1090

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: Two methods for including the effects of electron correlation on the electron density distributions of molecules are compared. Second-order Møller–Plesset perturbation theory (MP2) is shown to give electron density distributions in good qualitative agreement with much more time-consuming configuration interaction calculations. The latter include all single and double substitutions from the Hartree–Fock reference configuration. The two methods are compared by means of difference density maps calculated with large basis sets for a few representative molecules. From an analysis of the relative importance of single and double substitutions, it is shown that double substitutions are dominant near nuclei, but in other regions of space the single substitutions are more important. The MP2 method is shown to provide a practical method for calculating the correlation corrections to the electron density distributions of molecules of intermediate size.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.456162

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The effect of electron correlation on the topological and atomic properties of the electron density distributions of molecules (1989)

Boyd, Russell J. ; Wang, Liang-Chen

New York, NY [u.a.] : Wiley-Blackwell

Journal of Computational Chemistry 10 (1989), S. 367-375

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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 topological properties of the electron density and the properties of an atom in a molecule are calculated by means of second-order Møller-Plesset perturbation theory (MP2) and compared with the results of configuration interaction calculations (C12) which include all single and double substitutions from the Hartree-Fock reference configuration. A software package for analyzing the effects of electron correlation on the topological properties of the electron density of molecules is described. H2CO is used to provide a numerical example and to indicate that the number of bond critical points is unaffected by the inclusion of electron correlation. Correlation leads to only a small shift in the positions of bond critical points and a small change in the electron density at bond critical points. It is further shown that the energy of an atom in a molecule can be calculated to an accuracy of 1 kcal/mol and the electron population of an atom to about 0.001e. A statistical method is used to show that the deviation of the MP2 correlation correction relative to the CI2 correlation correction for a variety of atomic properties is about 25%.

Additional Material: 1 Ill.