A second order MCSCF method for large CI expansions

Abstract

A second order MCSCF method is presented in a form which is suitable for large CI expansions. This methodology allows one to employ second order MCSCF theory to problems in which the CI expansion is an order of magnitude larger than could be addressed previously. Sample calculations are reported on the X 1Σ+ and 2 1Σ+ states of HF in which the MCSCF wave function was composed of 1436 CSFs. (AIP)