Self-Consistent Band Structure of Niobium at Normal and Reduced Lattice Spacings

Self-consistent augmented-plane-wave energy-band calculations have been carried out for niobium for (a) normal lattice constant, α=1 exchange, (b) normal lattice constant, α=2/3 exchange, and (c) 5% reduced lattice constant, α=2/3 exchange. At normal lattice constant, α=2/3 exchange, an occupied s-d-band width of 0.387 Ry is found, in very good agreement with both L and M soft-x-ray emission experiments. The calculated density of states at the Fermi energy is 28.2 states atom^-1 Ry^-1, corresponding to a McMillan enhancement factor of 1.6. The Fermi surface consists of hole ellipsoids centered at N, a large hole octahedron centered at Γ, and a multiply connected "jungle gym," similar to that calculated by Mattheiss. The largest difference between experimental and calculated areas is less than 15%.