Electronic structure of the (2×2)C ρ4g carbidic phase on Ni{100}

Angle-resolved photoemission measurements of the valence-electronic structure of the Ni{100}(2×2)C structure are compared with the results of self-consistent density-functional calculations of the two-dimensional band structure for a c(2×2)C overlayer on Ni{100}. Good agreement is found for the energies of the main C 2p– and C 2s–related features at Γ¯ and the computed dispersion is similar to, but somewhat greater than, that observed experimentally. These experimental features map in the c(2×2) surface Brillouin zone defined by the carbon overlayer, and not the (2×2) zone of the surface reconstruction. Changes in the d band structure are attributed to this reconstruction and are not found in the calculated bands or in experiments on a c(2×2)O overlayer, both of which involve unreconstructed surfaces.