All-electron quasiparticle self-consistent GW band structures for SrTiO3 including lattice polarization corrections in different phases

The electronic band structure of SrTiO₃ is investigated in the all-electron quasiparticle self-consistent GW (QSGW) approximation. Unlike previous pseudopotential-based QSGW or single-shot G₀W₀ calculations, the gap is found to be significantly overestimated compared to experiment. After putting in a correction for the underestimate of the screening by the random phase approximation in terms of a 0. 8 approach, the gap is still overestimated. The 0. 8 approach is discussed and justified in terms of various recent literature results including electron-hole corrections. Adding a lattice polarization correction (LPC) in the q0 limit for the screening of W, agreement with experiment is recovered. The LPC is alternatively estimated using a polaron model. We apply our approach to the cubic and tetragonal phases as well as a hypothetical layered postperovskite structure and find that the local density approximation (LDA) to GW gap correction is almost independent of structure.