MOLECULAR CHEMISORPTION OF OXYGEN ON CU(100), NI(100) AND PT(111)

The electron structure of the oxygen molecule chemisorbed on metals is investigate using a sem empiric embedded cluster scheme. The influence of the metal d band for the interaction and the charge transfer is found to be qualitatively different for the Cu(100) surface compared to the transition metal surfaces Ni(100) and Pt(111). For Cu the metal s states are most important for the charge transfer from the surface to the pi* orbital of oxygen, while for Ni and Pt the metal d states play the dominant role. In a projected density analysis, it is demonstrated that the different location of the d-band for these substrates is crucial for the interaction between the oxygen pi* orbital and the metal orbitals. In the case of O2/Pt(111), the pi*-d hybridization results in a significant fraction of unoccupied density of states, which is consistent with experimental observations.