Premium
A practical valence bond method: A configuration interaction method approach with perturbation theoretic facility
Author(s) -
Song Lingchun,
Wu Wei,
Zhang Qianer,
Shaik Sason
Publication year - 2004
Publication title -
journal of computational chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.907
H-Index - 188
eISSN - 1096-987X
pISSN - 0192-8651
DOI - 10.1002/jcc.10382
Subject(s) - excited state , valence bond theory , perturbation theory (quantum mechanics) , valence (chemistry) , configuration interaction , chemistry , excitation , computer science , generalized valence bond , computational complexity theory , computational chemistry , bond length , bond order , electron , algorithm , physics , atomic physics , molecule , quantum mechanics , atomic orbital
The previously developed valence bond configuration interaction (VBCI) method (Wu, W.; Song, L.; Cao, Z.; Zhang, Q.; Shaik, S., J. Phys. Chem. A, 2002, 105, 2721) that borrows the general CI philosophy of the MO theory, is further extended in this article, and its methodological features are improved, resulting in three accurate and cost‐effective procedures: (a) the effect of quadruplet excitation is incorporated using the Davidson correction, such that the new procedure reduces size consistency problems, with due improvement in the quality of the computational results. (b) A cost‐effective procedure, named VBCI(D, S), is introduced. It includes doubly excited structures for active electrons and singly excited structures for inactive pairs. The computational results of VBCI(D, S) match those of VBCISD with much less computational effort than VBCISD. (c) Finally, a second‐order perturbation theory is utilized as a means of configuration selection, and lead to considerable reduction of the computational cost, with little or no loss in accuracy. Applications of the new procedures to bond energies and barriers of chemical reactions are presented and discussed. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 472–478, 2004