The optimized‐basis‐set multiconfiguration spin‐coupled method for the ab initio calculation of atomic and molecular electronic wave functions

Abstract

AbstractAn ab initio method for the calculation of atomic and molecular electronic wave functions is presented. The “Optimized‐Basis‐Set Multiconfiguration Spin‐Coupled” (OBS–MCSC) method may be viewed either as a multiconfiguration generalization of the spin‐coupled approach or as a nonorthogonal variant of the MCSCF method. In addition, the OBS–MCSC method optimizes the basis‐set exponential parameters simultaneously with all other variational parameters, through a second‐derivative minimization procedure. Explicit analytic expressions for the required first and second derivatives of the energy with respect to all variational parameters are obtained. Test calculations prove the capability of the method to yield compact yet accurate electronic wave functions.© 1993 John Wiley & Sons, Inc.