SURFACE BAND STRUCTURES ON NB(001)

We report the joint studies of experimental and theoretical surface ba nd structures of Nb(001). Angle-resolved photoelectron spectroscopy wa s used to determine surface-state dispersions along three high-symmetr y axes ($$$) over bar Gamma M, ($$$) over bar Gamma X, and ($$$) over bar MX in the surface Brillouin zone. Ten surface bands have been iden tified. The experimental data are compared to self-consistent pseudopo tential calculations for the ii-layer Nb(001) slabs that are either bu lk terminated or fully relaxed (with a 12% contraction for the first i nterlayer spacing). The band calculations for a 12% surface-contracted slab are in better agreement with the experimental results than those for a bulk-terminated slab, except for a surface resonance near the F ermi level, which is related to the spin-orbit interaction. The charge profiles for all surface states or resonances have been calculated. S urface contraction effects on the charge-density distribution and the energy position of surface states and resonances will also be discusse d.