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Limitations of roby'stheorem
Author(s) -
Cusachs L. C.,
Aldrich H. S.,
Aiken J. G.,
Jonassen H. B.,
Wheelock K. S.
Publication year - 2009
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.560090833
Subject(s) - atomic orbital , basis (linear algebra) , molecular orbital , physics , matrix (chemical analysis) , computational chemistry , atomic physics , theoretical physics , electron , mathematics , quantum mechanics , chemistry , molecule , geometry , chromatography
Roby'stheorem establishes that, under certain conditions, electron interaction matrix elements over symmetrically orthogonalized (Löwdin) orbitals may be obtained from those over the ordinary nonorthogonal basis by simply discarding all integrals containing products of orbitals centered on different atoms (nddo approximation). We present evidence of the existence of many important cases where the error of this approximation, in practice, varies so rapidly with internuclear distance as to constitute a serious problem.