title: Insights into the Electronic Structure of Molecules from Generalized Valence Bond Theory.
abstract: In this article we describe the unique insights into the electronic structure of molecules provided by generalized valence bond (GVB) theory. We consider selected prototypical hydrocarbons as well as a number of hypervalent molecules and a set of first- and second-row valence isoelectronic species. The GVB wave function is obtained by variationally optimizing the orbitals and spin coupling in the valence bond wave function. The GVB wave function is a generalization of the Hartree-Fock (HF) wave function, lifting the double occupancy restriction on a subset of the HF orbitals as well as the associated orthogonality and spin coupling constraints. The GVB wave function includes a major fraction (if not all) of the nondynamical correlation energy of a molecule. Because of this, GVB theory properly describes bond formation and can answer one of the most compelling questions in chemistry: How are atoms changed by molecular formation? We show that GVB theory provides a unified description of the nature of the bonding in all of the above molecular species as well as contributing new insights into the well-known, but poorly understood, first-row anomaly.
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign , 600 S. Mathews Avenue, Urbana, Illinois 61801, United States.
authors.forename: Thom H
authors.initials: TH
authors.lastname: Dunning
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign , 600 S. Mathews Avenue, Urbana, Illinois 61801, United States.
authors.forename: Lu T
authors.initials: LT
authors.lastname: Xu
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign , 600 S. Mathews Avenue, Urbana, Illinois 61801, United States.
authors.forename: Tyler Y
authors.initials: TY
authors.lastname: Takeshita
authors.affiliation: Department of Chemistry, University of Illinois at Urbana-Champaign , 600 S. Mathews Avenue, Urbana, Illinois 61801, United States.
authors.forename: Beth A
authors.initials: BA
authors.lastname: Lindquist