Self-Consistent Warped-Muffin-Tin-Potential Energy Bands ofγ−Fewith Various Exchange Approximations

Using a modified augmented-plane-wave expansion recently developed by us, we have calculated the energy bands and the binding energy of fcc $\gamma -\mathrm{F}\mathrm{e}$. From a self-consistently calculated muffin-tin charge density, we obtained a warped-muffin-tin potential. We used the full, $\frac{7}{9}$, and $\frac{2}{3}$ Slater exchange potentials. All gave reasonable energy bands but when the "Koopmans corrections" recently suggested by Herman et al. were added, the $d$ levels were driven below the $s$ levels at all points in the Brillouin zone and an unphysical type of $s-d$ hybridization was obtained.