Shifts in the Electronic Band Structure of Metals Due to Non-Muffin-Tin Potentials

The generally neglected potential outside the muffin-tin spheres induces average energy shifts of the order of 0.005 to 0.010 Ry in fully relativistic, high-symmetry levels of fcc palladium, fcc platinum, and bcc uranium. The high band mass of these transition metals combined with such shifts can cause errors of the order of 5% in predicting the Fermi radii. The splitting of the spin-orbit doublets is found to be insensitive to the inclusion of the outside of the muffin-tin potential. By augmenting a phase-shift parameter set with two or three effective pseudopotential coefficients which represent the effect of the weak added potential, an ab initio band structure may be used to fit accurate experimental data.