Approximate range-separated DFT for the band structure of complex materials

In recent years simulations based on range-separated exchange-correlation functionals in density functional theory have emerged as alternative to traditional GW and GW/BSE calculations in the determination of accurate quasi-particle band gaps [1] and excitonic features of materials [2]. Compared to local functionals, such computations are much more demanding in terms of computer time due to the incorporation of exact exchange.

In this contribution, we summarize recent advances in the development of range-separated functionals for the density functional based tight-binding method (LC DFTB) [3]. LC-DFTB and its time-dependent extension TD-LC-DFTB [4] provide accurate results for molecular systems at highly reduced computational cost with respect to first principles DFT. Here we present first results for the implementation of LC-DFTB using periodic boundary conditions with proper Brillouin zone sampling. This opens up the possibility to study the band structure of complex materials with large unit cells.

[1] L. Musen, J.R. Reimers, M.J. Ford, R. Kobayashi, R.D. Amos, J. Comp. Chem. 42 1486 (2021)

[2] S. Refaely-Abramson, M. Jain, S. Sharifzadeh, J.B. Neaton, L. Kronik, PRB 92 081204(R) (2015)

[3] V. Lutsker, B. Aradi, and T.A. Niehaus, J. Chem. Phys. 143 184107 (2015)

[4] J.J. Kranz, M. Elstner, B. Aradi, T. Frauenheim, V. Lutsker, A.D. Garcia, T.A. Niehaus, J. Chem. Theory Comput 13 1737 (2017)