Electron Energy Levels inCu3Au

Electron energy levels in perfectly ordered ${\mathrm{Cu}}_3$Au have been calculated using the modified-plane-wave (MPW) method for the majority of points in the Brillouin zone and using the orthogonalized-plane-wave (OPW) method for some of the lower symmetry points. The calculation has been done for the equivalent of 512 points in the reciprocal-space lattice. A muffin-tin model potential has been used. This was constructured from the atomic potentials of Herman and Skillman who did a self-consistent calculation based on the Slater version of the Hartree-Fock equations. This version includes an averaged exchange term. $E\left(\mathrm{k}\right)$ curves are shown. The Fermi level has been computed to be -0.39 Ry. The resulting Fermi surface compares very well with the simplified surface constructed by Harrison by folding the copper Fermi surface in accord with the new lattice. Calculations were also carried out at a limited number of points for copper using both the Herman-Skillman and the Chodorow potentials in order to examine the sensitivity of the results to difference in potential. The two compare within about 0.04 Ry near the Fermi level but some $d$-like points differ by as much as 0.1 Ry.