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On the optimal mixing of the exchange energy and the electron‐electron interaction part of the exchange‐correlation energy
Author(s) -
Gritsenko Oleg V.,
Van Leeuwen Robert,
Baerends Evert Jan
Publication year - 1996
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/(sici)1097-461x(1996)60:7<1375::aid-qua19>3.0.co;2-3
Subject(s) - kinetic energy , chemistry , electron , bond dissociation energy , electronic correlation , ab initio , exchange interaction , atomic physics , ab initio quantum chemistry methods , electron pair , interaction energy , dissociation (chemistry) , bond energy , molecule , molecular physics , physics , condensed matter physics , quantum mechanics , organic chemistry , ferromagnetism
Abstract The optimal mixing coefficient C of the exchange energy E x and the electron‐electron interaction part of the exchange‐correlation energy W 1 xc in the formula for the total exchange‐correlation energy E xc was expressed through the ratio of the kinetic T c and potential W c contributions to the correlation energy E c . This expression can be derived from a Heavyside step function model of the dependence of W λ xc on the coupling parameter of the electron interaction λ. Values of T c and W c obtained from ab initio wave functions were used to estimate C for a number of atoms and molecules. A strong dependence of T c , W c , and C on the bond distance was demonstrated for the case of the H 2 molecule. T c and C approach zero in the bond‐dissociation limit; so for an electron‐pair bond, the admixing of exact exchange to obtain an accurate E xc is strongly dependent on the bond length and has to disappear for weak interaction/large bond distances. The potential of the exchange‐correlation hole constructed for H 2 from an ab initio second‐order density matrix was compared with its generalized gradient approximation (GGA). © 1996 John Wiley & Sons, Inc.