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The origin of energy functional in Roothaan open shell SCF theory

✍ Scribed by G. T. Klimko; M. M. Mestechkin; B. N. Plakhutin; G. M. Zhidomirov; R. A. Evarestov

Publisher
John Wiley and Sons
Year
1990
Tongue
English
Weight
819 KB
Volume
37
Category
Article
ISSN
0020-7608

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✦ Synopsis

Abstract

Different methods of averaging of energy over the states of electronic configurations γ^N^ (n~γ~ = 1, 2, 3 and N = 1, 2, …, 2__n__~γ~ − 1) leading to Roothaan' energy expression are considered. The consequent values of vector coupling coefficients (VCC) in energy functionals for various states as well as for average values of energy are presented.

It is shown also that in molecular systems of cubic and tetragonal symmetry having electronic configurations t^N^ (N = 2–4) and e^2^ there exist states for which VCC are dependent on the choice of basis set of degenerate open‐shell molecular orbitals. The origin of such “non‐Roothaan” terms and peculiarities of its calculation by the restricted Hartree–Fock method are discussed.

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