Bonding of oxygen on aluminum: Relation between energy-band and cluster models

Abstract

A study of some factors which influence the position and shape of the resonance bands of adsorbates on surfaces is presented with emphasis upon the case of oxygen chemisorbed on aluminum. A twofold approach has been taken to determine the relative roles of local and delocalized electron effects: the energy-band structure for a thin film geometry is correlated with the eigenvalue spectrum from a "surface-molecule" cluster model. Oxygen resonance features are found to depend mainly upon a bond mechanism involving orbitals directed parallel to the surface such that the local bonding in the cluster model provides a reasonable description of the resonance position. Delocalization of the substrate electrons in the plane is found to provide a bulklike background against which the localized resonance is observed.