Combining mBJ exchange potential and bootstrap kernel of TDDFT to compute optical spectra of solids

Abstract

One of the fundamental challenges in calculating the optical properties of crystalline materials is the accurate description of exciton effects so as to make it computationally viable for studying large systems. We combine the modified Becke-Johnson (mBJ) exchange potential and bootstrap kernel (BSK) of time-dependent density functional theory (TDDFT) to compute the imaginary part of the dielectric function of a variety of semiconductors and insulators (Si, GaAs, NiO, TiO2, LiF, LiCl, SrTiO3 and NaMgF3). The results are compared with the experimental data available in the literature. We also compute their dielectric functions using the random phase approximations (RPA) to verify the effect of the BSK method on the optical spectra of these compounds. We conclude that TDDFT+BSK+mBJ calculations can determine the optical spectra of the solids in good agreement with the experimental data (except for small-energy gap materials such as Si and GaAs) with low computational cost, and using a fully ab initio procedure.