Electronic exchange, many body effects issues on first principle calculations of bulk silicon carbide (SiC) polytypes
Kamel Demmouche, Centre Universitaire Belhadj Bouchaib Ain Temouchent, Ain Temouchent, AlgeriaJosé Coutinho, University of Aveiro, Aveiro, Portugal
The first-principles Projector Augmented Wave method (PAW) is used to investigate the electronic, phonon band structure and dielectric properties of four bulk silicon carbide (SiC) polytypes. We employ PAW pseudopotential density functional theory with PBE and hybrid HSE06 approximations of the exchange-correlation functional. Many body effects are incorporated using the GW approximation of the self-interaction to study SiC properties. GW method in its single-shot variant, and which is based on the many body perturbation theory (MBPT), is used to calculate the quasi-particle (QP) energies of the band structure and the dielectric properties for different polytypes. The electronic band structure determination within GW method uses the Wannier procedure where a basis set of maximally localized Wannier functions (MLWF) is constructed to interpolate the QP energies of few regular mesh k-points to the high symmetry lines in Brillouin zone. As a consequence of QP correction to the Kohn-Sham energies band gap is increased by up to 3 eV in case of 4H-SiC, as compared to PBE band gap. GW results are comparable to those of hybrid functionals and are in good agreement with experimental results. The optical properties are then studied within PBE, HSE06 and including many body effects. In addition, phonon band structure has been investigated within HSE06 and compared to previous PBE results. We found good agreement with theoretical and experimental available data.