Choosing tight-binding models for accurate optoelectronic responses

Tight-binding models provide great insight and are a low-cost alternative to ab initio methods for calculation of a material's electronic structure. These models are used to calculate optical responses, including nonlinear optical effects such as the shift current bulk photovoltaic effect. The validity of tight-binding models is often evaluated by comparing their band structures to those calculated with density functional theory. However, we find that band structure agreement is a necessary but not sufficient condition for accurate optical response calculations. We compute the shift current response and dielectric tensor using a variety of tight-binding models of MoS2, including both Slater-Koster and Wannier tight-binding models that treat the Mo 4d orbitals and/or S 3 p orbitals. We also truncate hoppings in the Wannier function models to next-nearest-neighbor, as is common in tightbinding methods, in order to gauge the effect on optical response. By examining discrepancies in energies and optical matrix elements, we determine the interpolation quality of the different tight-binding models and establish that agreement in both band structure and wave functions is required to accurately model optical response.