Exact exchange-potential band-structure calculations by the LMTO-ASA method: MgO and CaO.

Abstract

We present a method for electronic band-structure calculations based on the density-functional formalism using, instead of the exchange potential in the local-density approximation (LDA), the exact Kohn-Sham density-functional exchange potential. The method is formulated within the linear muffin-tin-orbital method in the atomic-sphere approximation. We apply the method to the alkaline-earth oxides MgO andCaO. The obtained band gaps, 7.77 eV for MgO and 7.72 eV for CaO, are closer to the experimental values of 7.83 and 7.09 eV, respectively, while the corresponding LDA band gaps of 4.64 and 4.30 eV are too small. To our knowledge, the exact exchange potential is first applied to realistic solids. The exact exchange potentials thus calculated show structures well reflecting the atomic shells.