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Overlap repulsion with Löwdin's pairing theorem *
Author(s) -
Hamza A.,
Mayer I.
Publication year - 2001
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 - 10.1002/1097-461x(2001)82:2<53::aid-qua1029>3.0.co;2-b
Subject(s) - pairing , intramolecular force , atomic orbital , intermolecular force , open shell , chemistry , molecular orbital , charge (physics) , orbital overlap , basis (linear algebra) , physics , molecule , quantum mechanics , electron , atomic physics , mathematics , geometry , superconductivity
Using Löwdin's pairing theorem one can obtain an explicit expression for the overlap repulsion of two “unperturbed” closed‐shell molecules at the single determinant level. After some regrouping, the interaction energy can be presented as a sum of terms of different physical meaning, each of which is expressed explicitly in terms of the (paired) molecular orbitals of the interacting molecules. The interaction energy can be decomposed into the following terms: the “naive” electrostatic interaction corresponding to undisturbed charge distributions of the two molecules; the Hartree–Fock exchange calculated neglecting the orbital overlap; “finite basis” terms originating from the deviation of the individual molecular orbitals (MOs) from the Hartree–Fock limit; overlap effects modifying the intramolecular energies as well as the electrostatic and exchange interactions; “true” overlap effects containing intermolecular overlap integrals and intermolecular charge distributions in the one‐ or two‐electron integrals. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 82: 53–59, 2001