Studies on the Alternant Molecular Orbital Method. I. General Energy Expression for an Alternant System with Closed-Shell Structure

Abstract

The alternant molecular orbital method is used to derive a general energy expression for an arbitrary alternant system with closed-shell structure. This expression exhibits a simple dependence on a single mixing parameter, minimization with respect to which yields the optimum energy. An analysis reveals the effectiveness of the method to depend on the relative magnitude of two quantities, one involving the one-electron operator energies and the other related to electron interaction integrals which connect the bonding with the antibonding orbitals from the simple ASMO scheme. Some comments on the method, in the light of the results obtained, are added.