First principles study of benzene adsorption on transition metal surfaces

Abstract

In this work, state-of-the-art molecular modeling is used to systematically study this process. First, numerically converged low coverage adsorption energies of -107 kJ/mol for the bridge site and -71 kJ/mol for the hollow site of the Pt(111) surface were calculated at the Density Functional Theory-Perdew Burke Enzerhoff (DFT-PBE) level of theory. Second, the accuracy of the DFT-PBE description of the electronic interaction between benzene and Pt was investigated. Though the DFT-PBE theory accurately describes the electronic structure of the Pt(111) surface and the HOMO of benzene, it significantly underestimates the stability of the LUMO of benzene. As a result, DFT-PBE significantly underestimates the effect of back-donation on the adsorption energy. Correlated wave-function-based methods such as MP2 and CCSD(T) indeed predict a 50 to 60 kJ/mol stronger adsorption of benzene at the hollow site of a small Pt3 cluster.