Electronic energy level structure calculations of chemisorbed CO on Ni (100)

Abstract

Our cluster model calculations, using the self−consistent statistical exchange (Xα) scattered wave method, yield three main peaks in the ultraviolet photoemission spectrum of CO chemisorbed on Ni (100). This is consistent with the experimental observations. However, our calculations imply rather large bonding and relaxation shifts. The molecular orbitals 5σ and 1π of CO are found to interact with the metal 3d, in addition to 4s and 4p orbitals, contrary to some previous suggestions. Furthermore, we predict a chemisorption level near the top of the Fermi level, which presumably has not been detected experimentally due to interference with the high density of Ni d−states. A possible mechanism for CO bonding which emerges from our calculations is discussed.