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Studies in the paired orbital method. I
Author(s) -
Pauncz R.,
Kirtman B.,
Palke W. E.
Publication year - 1987
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.560320752
Subject(s) - atomic orbital , basis set , molecular orbital , wave function , physics , generalization , chemistry , atomic physics , molecular physics , molecule , quantum mechanics , mathematics , mathematical analysis , electron
An extension of the alternant molecular orbital method to nonalternant molecules is presented. The key step involves generation of a set of localized virtual orbitals that are paired to the localized occupied orbitals ( LMO ' S ). Each of the paired virtuals is required to occupy the same region of space as the corresponding LMO by applying a generalization of the Edmiston–Ruedenberg localization criterion. Illustrative calculations are reported for the water molecule. Using a double‐zeta basis, it is found that the new paired orbital ( PO ) method gives approximately 20% of the available correlation energy at R = R e , 1.5 R e , and 2 R e . We speculate that the PO wave function may provide a good initial approximation for a subsequent many‐body perturbation treatment.