Ab initio GW-Bethe-Salpeter Equation Approach using Optimally Tuned Range-Separated Hybrid Functionals and Non-Uniform Reciprocal Space Sampling

One of the gold standard methods for predictive calculation of optical properties of solids is the ab initio GW-Bethe Salpeter equation (GW-BSE) approach. Two challenges in predicting excited state properties within the GW-BSE framework are the input Kohn-Sham eigensystem (or “starting point”) and the reciprocal space sampling of the exciton wavefunction. Recently, the Wannier-localized optimally tuned screened range separated hybrid (WOT-SRSH) functional [1] has been shown to be an excellent starting point eigensystem for “single shot” ab initio G0W0 and G0W0-BSE calculations [2,3]. Moreover, when solving the BSE, it is now possible via Wannier interpolation to finely sample the exciton wavefunction in nonuniform regions of reciprocal space [4] even when using hybrid functionals as a starting point, avoiding the need for an extremely dense uniform grid. Here, we present absorption spectra and excited state properties, including exciton binding energies, for prototypical semiconductors and halide perovskites computed using the GW-BSE framework with a WOT-SRSH starting point, solving the BSE with a dense nonuniform reciprocal space sampling. We discuss the convergence of our results relative to prior calculations and compare with experiments.

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

[2] G. Ohad, S. E. Gant, et al., arXiv:2309.02117 (2023).

[3] S. E. Gant, et al., Phys. Rev. Materials 6, 053802 (2022).

[4] A. Alvertis, A. Champagne, et al., Submitted (2023).