Role of semicore d electrons in quasiparticle band-structure calculations

We have investigated the role of semicore $d$ electrons in the calculation of quasiparticle band structures within the $\mathrm{GW}$ approximation for a number of elemental and compound semiconductors, as well as for a semimetal. The systems studied comprise Ge, GaN, ZnS, CdS, and $\ensuremath{\alpha}$-Sn. Semicore $d$ states are explicitly taken into account as valence states in our investigations. Overall, they have a strong influence on the band structure of the compounds, but not on that of the elemental semiconductor Ge or of the semimetal $\ensuremath{\alpha}$-Sn. Nevertheless, there is a distinct influence on the Ge band structure to be noted, as well, in that the gap changes from direct to indirect by the inclusion of the semicore $d$ states. Our band-structure results are in very gratifying agreement with available experimental data.