Accurate defect electronic structure from non-empirical range-separated hybrid functionals: the case of oxygen vacancies in ZnO

Defects in semiconductors can act as a knob for tuning properties or as an undesirable feature affecting semiconductor performance. Density functional theory with semilocal functionals can fail to predict defect properties and absolute valence band maximum energies due to delocalization errors, leading to inaccurate defect level alignment. Here, we apply a recently developed nonempirical Wannier-localized optimally-tuned screened range-separated hybrid (WOT-SRSH) functional [1] to properties of the oxygen vacancy in zinc oxide, a well-studied defect. We show that in addition to quantitatively capturing the wurtzite ZnO band gap, our WOT-SRSH calculations predict an accurate absolute valence band maximum energy. Moreover, we show the bulk WOT-SRSH parameters are transferable to point defects, and lead to predictions of oxygen vacancy charge transition levels in good agreement with experiments and prior calculations with empirically-tuned hybrid functionals. We discuss the implications for broader application of the WOT-SRSH approach and the transferability of bulk nonempirical parameters to defects in other systems.