Crystal structures and band gap characters of h-BN polytypes predicted by the dispersion corrected DFT and GW method

Geometry optimizations are performed for three polytypes of h-BN using density functional theory with dispersion correction for the van der Walls interaction. Quasiparticle band structure calculations are carried out to solve the controversy on band gap type of h-BN. Band energies are corrected by GW method. The h-BN with Bk structure has an indirect band gap of 5.840 eV. Two kinds of h-BN polytypes are shown to be mechanically stable and have quasi-direct band gap type.