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 l^N most mechanisms of configuration interaction lead to a simple scaling of the crystal field parameters B_q^k. However, one‐electron excitations, either from the l^N shell to unfilled orbitals or from closed shells into the l^N shell, result in a scaling of the Slater integrals F^k and in overt effects that cannot be accommodated by the B_q^k 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.