GVB-RP: A reliable MCSCF wave function for large systems

Abstract

We have developed a version of generalized valence bond (GVB) that overcomes the major weakness of the perfect pairing approximation without requiring a full transformation of the integrals at each step of the self-consistent orbital optimization. The method, called generalized valence bond–restricted pairing (GVB–RP), describes properly the dissociation of up to triple bonds and provides smooth potential energy surfaces for most chemical reactions. The wave functions obtained are a good starting point for more sophisticated computational techniques. The applicability of the method is illustrated with a few simple examples including multiple-bond dissociations, transition states for symmetry allowed, symmetry forbidden, and radical reactions, as well as reactions at a transition-metal center. The cost of the method compares well with other self-consistent correlated techniques. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 73: 1–22, 1999