Molecular Calculations. II. Methods of Approximation of Molecular Integrals

A description is given of the integral approximations used in the LCAO MO self-consistent field treatment of H2O reported in the preceding paper. The estimation of electronic repulsion integrals by replacing one of the electron charge distributions by a point charge is considered in detail and found...

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Bibliographic Details
Published in:The Journal of chemical physics 1955-12, Vol.23 (12), p.2358-2365
Main Author: Ellison, Frank O.
Format: Article
Language:English
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Summary:A description is given of the integral approximations used in the LCAO MO self-consistent field treatment of H2O reported in the preceding paper. The estimation of electronic repulsion integrals by replacing one of the electron charge distributions by a point charge is considered in detail and found to be reliable in certain general cases. A modification of the Sklar approximation is developed which is applicable to integrals involving 1saχb, in which μ(1sa) (effective Z) is small and μ(χb) is large. A method is described for securing a better ``corrected'' Mulliken approximation of exchange integrals. The estimation of unsymmetrical nuclear attraction integrals is carried out by using uniformly charged spheres of finite size to represent AO distributions. This method is compared with the Mulliken and Löwdin approximations.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.1741880