Core polarization in solids: Formulation and application to semiconductors

Accurate treatment of exchange and correlation effects involving core and valence electrons can be surprisingly important in solid-state calculations, especially for solids having elements with shallow core electrons, such as Ga and Ge. A local-density-approximation treatment of core-valence interactions leads to errors of $\sim 0.4\mathrm{eV}$ for key features in the band structures of Ge and GaAs, even when valence-valence interactions are treated in a first-principles, quasiparticle approach. We apply a core-polarization-potential treatment of core-valence interactions within the framework of such quasiparticle calculations. Final results have errors of $\sim 0.1\mathrm{eV}$ in band-energy differences.