Subspace effective potential theory for configuration interaction

Abstract

In this article we present an approach which combines the configuration interaction methodology and orbitals derived via single particle equations with a local potential V eff , the variational parameters of which are determined by minimizing the so-called subspace functional instead of the traditional single energy functional EðUÞ5 < UjHjU >. In this way ground and excited states orbitals are put on equal footing. The V eff is restricted to have the form of a model potential expressed in terms of the external potential. One of the advantages of the present direct mapping formulation, is that the effective potential, V eff , has the symmetry of the external potential. Applications are focused mainly on excited states of the HeH and BeH molecules having spatial and spin symmetries as those of the ground one.