Selected dissociation- and correlation-consistent configuration interaction by a perturbative criterion

Abstract

We propose a perturbative criterion to select the most important dissociation- or correlation-consistent type of contributions to perform generalized valence bond-configuration interaction (GVB-CI) calculations, dissociation-consistent configuration interaction (DCCI) or correlation-consistent configuration interaction (CCCI) approach, respectively. The procedure presented is computationally less demanding than the CCCI proposed by Goddard and co-workers. To ensure the distance consistency of the MOs used, the nonvalence virtual orbitals are obtained by a projection technique. The results obtained for a few test calculations show the ability of the suggested approach to get close results to full CI, DCCI, and CCCI values using a small CI expansion. It seems to be a promising way to treat correlation changes in large molecular systems which would be inaccessible by other methods.