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Extracting the hybrid functional mixing parameter from a GW quasiparticle approach



Relying on quasiparticle GW electronic structure calculations we present an approach to obtain an “optimal value” of the so called “mixing parameter,” α, in hybrid functional calculations. We show that when this “optimal” amount of exact exchange (we denote this as αopt) is mixed with the semi-local PBE exchange-correlation functional, the net quasiparticle corrections to the PBE Kohn–Sham eigenvalues attain a minimum value. We employ this approach to perovskite oxide insulators SrTiO3 and PbTiO3 and compare that to the widely studied semiconductor compounds, Si and Ge. A system dependence of the optimal choice of the mixing parameter is revealed.