Using valence bond methods to estimate intramolecular basis set superposition errors

Abstract

We show that a valence bond type wave function with non-orthogonal orbitals, and enforcing a restriction of which basis functions a given molecular orbital is allowed to be expanded in, can be used to estimate intramolecular basis set superposition errors. The method can be considered as a generalization of the valence bond strictly/extremely localized molecular orbital methods, or as a generalization of the strictly monomer molecular orbital, block-localized wave function, and absolutely localized molecular orbital approaches for intermolecular systems. The method underestimates charge transfer interactions but can be used to estimate the magnitude of basis set superposition errors for relative conformational energies.