Bonding of surface states on W(001): All-electron local-density-functional studies

Results of self-consistent all-electron full-potential linearized- augmented-plane-wave method local-density-functional calculations are presented for W(001) films consisting of 1, 3, 5, 7, 9, and 8 layers. The theoretical value of the work function for films with five and more layers is found to be within 0.05 eV of the experimental value of 4.63 eV. It is demonstrated that a film of seven layers is sufficiently thick to describe surface states and surface resonance states. An analysis of the dispersion and the change of bonding for the surface (resonance) states of » symmetry suggests that the discrepancies between experimental and theoretical surface energy band structures concerning surface states and surface-resonance states near the M» symmetry point are due to displacements of the surface atoms in the high-temperature phase of the W(001) system.