Self-consistent electronic structure of surfaces: Surface states and surface resonances on W(001)

Surface states (SS) and surface resonances (SR) on the W(001) surface have been determined from the first self-consistent energy-band study of this metal surface. The calculations were performed for a seven-layer film using our thin-film linearized augmented-plane-wave method which includes all relativistic corrections except the spin-orbit interaction. Self-consistency was found to be essential for obtaining an accurate value of the work function-4.5±0.2 eV, in excellent agreement with experiment. No evidence was found for surface core-level shifts as observed in photoemission from the (110) surface, indicating the possible importance of final-state effects. A complete description of all three experimentally observed resonance bands is given for the first time: SS and SR states are found to exist in different portions of the two-dimensional Brillouin zone; their location and symmetry are in very good agreement with structure observed in photoemission at 0.3, 0.8, and 4.2 eV below the Fermi energy, EF. Particularly interesting is the close agreement of the never before obtained k→=0 true SS (at - 0.3 eV) with experiment.