Calculation of the Fermi velocity in tungsten

The anisotropy of the Fermi velocity of tungsten has been calculated for different parts of the Fermi surface. The calculation was carried out by using the LMTO method in which the potential was constructed according to Mattheiss' rule with overlapping, relativistic atomic charge densities. In accordance with the experiments the results show that both magnitude and the anisotropy of the Fermi velocity are highest for the hole octahedron surface. For the other parts of the Fermi surface the value of the Fermi velocity is smaller, and it does not exceed a 50% change as a function of k.