Improved Method for Efficient Large-scale GW Calculations for 2D Systems

Accurate and efficient predictions of excited-states properties of complex materials remain a major challenge due to complication of the convergence issue and the unfavorable scaling of the computational cost with respect to the system sizes. GW calculations for 2D materials pose additional challenges due to the analytical behavior of the 2D dielectric function. Recently we have come up with an improved scheme that can significantly reduce the k-point density required in GW calculations for 2D materials. This method, when combined with our recently developed method [1] that greatly alleviates the burden of including a large amount of empty states in conventional GW calculations, can drastically reduce the computational costs for GW calculations for complex 2D materials. We have applied our new method to calculate the GW quasiparticle band structures of several 2D materials, including recently synthesized C₂N and C₃N. We will discuss the convergency behavior of the calculated quasiparticle band structure with respect to various sampling and cutoff parameters and compare our results with previous work, aiming at shedding some light on accurate and efficient GW calculations for two-dimensional materials. [1] W. Gao, W. Xia, X. Gao, and P. Zhang, Scientific Reports 6, 36849 (2016).