An anisotropic functional for two-dimensional material systems

We propose a exchange correlation potential for semiconductor materials, that is based on physical properties of the underlying microscopic screening. We demonstrate that it reproduces the low temperature band gap of several materials. Moreover, it respects the required linearity condition of the total energy with the fractional occupation number, as expressed by the generalized Koopman’s theorem. We show that this novel functional can be used as a kernel in linear response TDDFT to reproduce excitonic effects in optical spectra. We will discuss how to generalize such a functional to anisotropic systems like 2D materials. The presence of interfaces modifies the screening behavior in layered systems in a way, which cannot be described by HSE or any other screened exact exchange functional, which are based on assumptions of isotropy.