Configuration Interaction in Crystal Field Theory

Abstract

The effect of configuration interaction on the validity of the usual method of expanding the crystal field potential in terms of spherical harmonics is examined using second-order perturbation theory. It is found that for a configuration of equivalent electrons lN most mechanisms of configuration interaction lead to a simple scaling of the crystal field parameters Bqk. However, one-electron excitations, either from the lN shell to unfilled orbitals or from closed shells into the lN shell, result in a scaling of the Slater integrals Fk and in overt effects that cannot be accommodated by the Bqk parameters alone. As a result, the crystal field parameters can be expected to vary from one multiplet to another, even in the limit of Russell—Saunders coupling. The consequences of these overt configuration-interaction effects are discussed.