The importance of correlation effects on the bonding of atomic oxygen on Pt(111)

Abstract

The adsorption properties and the bonding nature of atomic oxygen adsorbed on the three-hollow sites of Pt9 and Pt25 cluster models of the Pt(111) surface have been studied by means of ab initio wave functions. Correlation effects have been introduced by various methods: single and multireference second-order perturbation theory, multireference configuration interaction, and density functional corrections to the Hartree–Fock energy using a variety of expressions of density functionals. While the adsorption and vibrational properties of adsorbed oxygen are sufficiently well described at the Hartree–Fock level, the adsorption energy is completely wrong as the system is unbound in the one-electron approximation while it is strongly bound at the correlated level. The use of correlation functional based on the Hartree–Fock density is not sufficient to obtain a correct estimate of the strength of the bond. We will also show that the bonding of oxygen to Pt has a partial ionic character and the effect of correlation is to enhance the importance of covalent contributions to the bonding.