Multiconfiguration Wavefunctions for Molecules: Current Approaches

Abstract

The generalized valence bond (GVB), fully optimized reaction space (FORS) and complete active space self-consistent field (CASSCF) methods are discussed. All of these approaches in their simplest form provide a multiconfiguration model for the electronic structure of molecules based on a well defined set of valence orbitals. As such they correct for a major deficiency in the Hartree-Fock model. While the GVB, FORS, and CASSCF methods permit the use of a larger orbital set, a scheme which provides a consistent description of molecular systems with an expanded set has yet to be developed.