Speeding-up GW calculations for 2D materials

GW approximation can properly describe the quasiparticle band structure of semiconductors and insulators beyond semi-local or hybrid density functional theory (DFT). For 2D materials, one of the computationally expensive part of a properly converged GW calculation is to finely sample the Brillouin zone in obtaining the non-interacting RPA polarizability, due to sharp dielectric features in 2D semiconductors. This difficulty in achieving convergence in k-point sampling becomes even more computationally expensive in modeling defects inside supercells at the GW level. We can speed up the GW-level defect calculations by using the polarizability of pristine 2D materials as an approximation, obtained from a unit-cell calculation and folded into a supercell Brillouin zone. Combining this method with the extrapolar technique [1] will further accelerate those calculations. We expect this method to be applied to high-throughput GW calculations for point defects in 2D materials with improved defect level placements and band gaps compared to DFT-level calculations.



[1] F. Bruneval, and X. Gonze, Physical Review B, 78(8), 085125 (2008).