Accurate band gaps and optical spectra of halides and oxides from a non-empirical, localization based optimal tuning of a screened range-separated hybrid functional

Accurate prediction of fundamental band gaps of crystalline solid-state systems, entirely within density functional theory, has been a long-standing challenge. Previously, we developed a simple and inexpensive method that achieves this by means of nonempirical optimal tuning of the parameters of a screened range-separated hybrid functional [1]. The tuning involves the enforcement of an ansatz that generalizes the ionization potential theorem to the removal of an electron from an occupied state described by a localized Wannier function in a modestly sized supercell calculation. Here we present applications of the method to more complex systems, notably halide perovskites and metal oxides. We demonstrate quantitative accuracy in band gaps and optical absorption spectra with respect to experiment and a comparable level of accuracy to many-body perturbation theory calculations. We further demonstrate the merit of using the optimally tuned eigensystem as a starting point in combined GW plus Bethe-Salpeter calculations.



[1] D. Wing et al., PNAS 118, e2104556118 (2021).