Differential correlation effects for states of the 3dnand 3dn4smconfigurations. I. The copper and zinc atoms and their ions

Abstract

The recently formulated approximate ab initio method for the evaluation of electron correlation effects on atomic energy differences, which has been tested for the first-row atoms, has been slightly modified to become applicable to transition-metal atoms and ions. Pilot calculations have been performed for: (a) the excitation energies in Cu, Cu+, Zn+ and Zn2+; (b) the electron affinity of Cu; and (c) the ionisation potentials for Cu, Cu+, Zn, Zn+ and Zn2+. The results indicate that the present approach leads to a satisfactory agreement with the observed values. The impact of various types of correlation effects is carefully studied. It turns out that for some of the energy differences even the correlation effects involving the 2p electrons may be important. The results are modified to take into account the leading relativistic corrections, which further improve the results.