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Subtle energies in density functional theory: Correlation and molecular dissociation
Author(s) -
March N. H.
Publication year - 1995
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.560560411
Subject(s) - diatomic molecule , density functional theory , pseudopotential , homonuclear molecule , heteronuclear molecule , chemistry , atomic physics , valence electron , dissociation (chemistry) , molecule , valence (chemistry) , physics , electron , quantum mechanics , computational chemistry
In nonrelativistic theory, heavy atoms with atomic number Z have binding energies that can be analyzed into a sum of decreasing terms: (i) the Hartree energy α Z 7/3 , (ii) a “boundary correction” α Z 2 due to Scott, and (iii) exchange energy in the Dirac‐Slater approximation α Z 5/3 . Correlation varies grossly linearly with Z and a density functional interpretation is proposed. Generalization to diatomic molecules is then considered, the total overlap population being now an important ingredient. Both heteronuclear and homonuclear molecules are treated. Attention is then focused on the molecular dissociation energy D : a further “subtle” quantity for density functional theory because of Teller's theorem. Following the proposal of Mucci and March, in light molecules with N electrons, D / N 2 is connected with the von Weizsäcker inhomogeneity kinetic energy T w ; this motivates a brief discussion of scaling properties of this latter quantity. Generalizing the treatment of atomic energies outlined above, the 1/6 power law relating D / N 2 with Tar is obtained. Finally, for the valence electrons only in alkali metal clusters, D / N is related to T w using pseudopotential calculations. © 1995 John Wiley & Sons, Inc.