A b i n i t i o self-consistent field and configuration interaction study of Cu5O and Ag5O as models for oxygen chemisorption on Cu(100) and Ag(100)

Abstract

The lowest electronic states of Cu5O and Ag5O arising from interaction of atomic oxygen (3P) and the isolated cluster model on the 2E or 4A2 electronic states have been studied at the SCF, CASCI, MP2, and CIPSI levels using nonempirical pseudopotentials for the Ar (Kr) cores of Cu (Ag). The ground state of Cu5O and Ag5O is found to be 2E but only after inclusion of correlation effects. However, the energy difference between 2E and the 4A2 or 2A1 electronic states is rather small. The effects of electronic correlation have been analyzed in terms of nondynamical and dynamical contributions. It is shown that SCF values account for only about 25%–30% of the total binding energy, whereas inclusion of nondynamical correlation contributions allow to recover 50% of that value. Thus, dynamical correlation effects must be included in order to describe properly oxygen-cluster interaction occurring in these systems. Results are in good agreement with recent all electron CI studies carried out for Cu5O (2E).