Self-consistent local-orbital method for calculating surface electronic structure: Application to Cu (100)

A method is introduced for computing the self-consistent electronic structure of solid surfaces or any other periodic defect array. Results are obtained for the Cu (100) surface. The computed electron work function is in excellent agreement with experiment. A large density of surface states is found to be split off from the upper $3d$-band edge. This large density of surface states has not been seen before theoretically, presumably because these states are sensitive to self-consistency. Surface-state and total-charge-density plots show that a significant fraction of the density in the surface layer is due to electrons in these surface states. Their existence is corroborated by photoemission difference spectra taken for chemisorbed nitrogen, oxygen, and sulfur on Cu (100). A prominent surface-state band among these states which was found theoretically has subsequently been isolated by angular photoemission. The dispersion and energy location of the experimental result agrees very well with the theoretical prediction. Further insight into surface-electronic-structure properties is provided by results for local and total densities of states as a function of film thickness, one to nine atomic layers.