Band gaps and dielectric functions of cubic and hexagonal diamond polytypes calculated by many-body perturbation theory

Abstract

Band structures for diamond polytypes are calculated by density functional theory with local density approximation and the band energies at high symmetry k-points are corrected using the GW method. The GW band gap energy is 5.627 eV for 3C-diamond, 4.683 eV for 2H-diamond, 5.983 eV for 4H-diamond, and 5.950 eV for 6H-diamond. For dielectric function calculations, electron–hole interaction is treated by the Bethe–Salpeter equation. Anisotropic dielectric response of hexagonal diamond polytypes is demonstrated and the 2H-diamond has significant anisotropic optical absorption property. Comparison with available experimental data for 3C-diamond and 2H-diamond is discussed.