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Charge fluctuations and correlation strength in chemical bonds: First‐row homonuclear diatomic molecules
Author(s) -
Yu M.,
Dolg M.,
Fulde P.,
Stoll H.
Publication year - 1998
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(1998)67:3<157::aid-qua3>3.0.co;2-u
Subject(s) - homonuclear molecule , chemistry , bond order , diatomic molecule , atomic orbital , localized molecular orbitals , electronic correlation , chemical bond , charge (physics) , atomic physics , valence bond theory , generalized valence bond , molecular physics , bond length , molecule , quantum mechanics , physics , electron , organic chemistry
We investigate, by means of ab initio calculations, the strength of electron correlations within covalent bonds: the first‐row homonuclear diatomics serve as test cases. As an appropriate measure of the correlation strength, we introduce the reduction of the mean‐square deviations of the electronic charges in localized orbitals forming a bond. A recently developed population analysis in terms of local operators derived from localized molecular orbitals is thereby used. The correlation‐strength parameter depends only weakly on dynamical correlations as test calculations demonstrate. Therefore, the full‐valence complete active space self‐consistent field (CASSCF) approximation is applied in order to study the changes in the correlation strength with changing bond length for different types of bonds. A number of simple rules emerge from this discussion. In addition, we show that charge fluctuations are not only a reliable measure of intrabond correlation effects, but also can be used to monitor intraatomic quasi‐degeneracy effects as well as the interdependence within multiple bonds. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 157–173, 1998