Brillouin{endash}Wigner based multi-reference perturbation theory for electronic correlation effects

Journal Article · Sun Mar 01 04:00:00 EST 1998 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.475921· OSTI ID:597191

Wenzel, W ^[1]; Steiner, M M ^[2]

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1. Theoretical Physics I, Dortmund University, D-44221 Dortmund (Germany)
2. Department of Physics, Ohio State University, 174 W 19th Ave, Columbus, Ohio 43210 (United States)

We investigate basis set reduction (BSR), a configuration-based multi-reference perturbation theory using an implicit effective Hamiltonian motivated by Brillouin-Wigner perturbation theory. This approach avoids the intruder-state and level-crossing problems by construction and yields a rapidly converging perturbation expansion. Formulated to systematically approximate multi-reference configuration interaction, BSR yields accurate results in second order, because it includes relaxation effects of the primary space wavefunction in the presence of the perturbation. We benchmark the method for molecules (CH{sub 2},O{sub 3}) in which both dynamical and non-dynamical correlation effects are known to be important, obtaining accuracies of the order of 1 kcal/mol across the potential energy surface in second-order perturbation theory. We address the critical issues of perturbative orbital optimization for the primary orbital space, the choice of the secondary orbital space and the effects of single excitations. {copyright} {ital 1998 American Institute of Physics.}

• OSTI ID: 597191
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 12 Vol. 108; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
CONFIGURATION INTERACTION
ELECTRON CORRELATION
ELECTRONIC STRUCTURE
METHYLENE RADICALS
OZONE
PERTURBATION THEORY
WAVE FUNCTIONS