All-electron mixed basisGWcalculations ofTiO2and ZnO crystals

Abstract

In transition metal oxide systems, there exists a serious discrepancy between the theoretical quasiparticle energies and the experimental photoemission energies. To improve the accuracy of electronic structure calculations for these systems, we use the all-electron mixed basis $\mathit{GW}$ method, in which single-particle wave functions are accurately described by the linear combinations of plane waves and atomic orbitals. We adopt the full $\ensuremath{\omega}$ integration to evaluate the correlation part of the self-energy and compare the results with those obtained by plasmon pole models. We present the quasiparticle energies and band gap of titanium dioxide (${\mathrm{TiO}}_{2}$) and zinc oxide (ZnO) within the one-shot $\mathit{GW}$ approximation. The results are in reasonable agreement with experimental data in the case of ${\mathrm{TiO}}_{2}$ but underestimated by about 0.6--1.4 eV from experimental data in the case of ZnO, although our results are comparable to previous one-shot $\mathit{GW}$ calculations. We also explain a new approach to perform $\ensuremath{\omega}$ integration very efficiently and accurately.