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Third‐order generalized Van Vleck perturbation theory variant of multireference perturbation theory for electron correlation
Author(s) -
Khait Yuriy G.,
Jiang Wanyi,
Hoffmann Mark R.
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.22008
Subject(s) - perturbation theory (quantum mechanics) , electronic correlation , perturbation (astronomy) , metastability , electron , physics , statistical physics , correlation , quantum mechanics , mathematics , geometry
A third‐order approximation to the generalized Van Vleck perturbation theory (GVVPT3) variant of multireference perturbation theory treatment of dynamic electron correlation is described. The approximation builds upon some aspects of the increasingly widely used GVVPT2, which we introduced previously (Khait et al., J Chem Phys 2002, 117, 4133). In addition, using formal relations obtained in connection with GVVPT3, a more thorough understanding of GVVPT2 is obtained, including a key diagnostic that assesses suitability of GVVPT2 for specific tasks. Computational aspects of the implementation of GVVPT3, especially the use of a macroconfiguration description of the model space, are described. The obtained GVVPT3 method can use both complete and incomplete model spaces efficiently. We demonstrate the new method on a series of model problems that demonstrate the applicability of the suggested approach. Among other tests, we show that GVVPT3 is capable of reproducing MRCISD results to within 0.01 eV for the problematic barrier height of the metastable N 2 2+ . © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009