Quasiparticle band structures of the 4d perovskite oxides SrZrO3 and BaZrO3

Although the challenge of GW calculations of the quasiparticle properties of 3d transition metal oxides (TMOs) is well recognized, TMOs involving 4d electrons may be considered borderline systems and have received less attention. Here we present the quasiparticle band structures of SrZrO3 and BaZrO3, two relatively simple wide band gap oxides for which accurate calculations of the electronic structure are scarce despite their technological importance. We show that fully converged GW calculations can accurately predict the quasiparticle properties of 4d TMO perovskites SrZrO3 and BaZrO3, regardless of the starting mean-field solution being calculated within straightforward density functional theory (DFT) or the DFT+U method. This is in contrast to the cases of 3d TMO perovskites SrTiO3 and BaTiO3, for which the DFT+U method is shown to provide a much better starting point for subsequent GW calculations. Compared with the fairly localized 3d states, the more extended 4d orbitals seem to be well described within DFT using local or semilocal functionals. Our results reaffirm the accuracy and robustness of the GW method provided that faithful zeroth-order mean-field solutions are available, and that the results are adequately converged.