The electronic structure of surfaces with the matching green function method: II. fcc and bcc transition metal surfaces

Using the matching Green function method, the densities of states at (001) surfaces of Ni (fcc) and Mo (bcc) are calculated. Fixing the wavevector parallel to the surface, the surface density of states at Ni(001) is similar to the bulk, with band edge singularities rounded off and reflected in big surface resonances. Changes are much greater in the case of Mo(001), and the surface density of states has a central peak in the minimum of the bulk density of states. This peak arises from the 4d level in the surface atoms interacting weakly with the substrate and with neighbouring surface atoms. Our results are compared with angular resolved photoemission theory and experiment — in the case of Ni all the experimental peaks correspond to bulk k-conserving transitions, though some surface resonances in the Mo surface density of states show up in photoemission.