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On the applicability of the screened‐Coulomb exchange model in Kohn–Sham density functional studies
Author(s) -
Proynov E. I.,
Salahub D. R.
Publication year - 1994
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/qua.560490202
Subject(s) - coulomb , kohn–sham equations , density functional theory , electron exchange , electron , physics , exchange interaction , spin density , conjugate , statistical physics , quantum mechanics , condensed matter physics , mathematics , mathematical analysis , ferromagnetism
The screened‐Coulomb exchange model used first in the X α method and later on in Kohn–Sham density functional theory is reexamined. Based on the well‐elaborated framework of the local spin‐density approximation, we show that this model is not well suited when systems with a finite number of electrons are concerned, because it does not respect the pair‐density sum rule. A proper modification of the model is proposed by reformulating it in terms of a screened‐exchange hole and ensuring the sum rule for this hole. As a result, it is shown how the static screened exchange in finite systems is accompanied by a conjugate antiscreened one. The possible consequences of this effect on the application of the screened‐Coulomb exchange model are discussed. © 1994 John Wiley & Sons, Inc.