GW approximation study of the Compton profile of ZnSe

We have obtained the Compton profile of ZnSe from the first principles GW approximation (GWA) method and ground-state density functional theory (DFT) method. We observe that between 0 and 1.5?a.u., there is better agreement to previous studies via the GWA difference profile compared to the ground-state difference profile. Above 1.5?a.u., both cases do not agree with the trend of the previous study; however, the application of the GWA is seen to improve the agreement compared to localized density approximation. Previous studies have reported that discrepancies from experiment are related to pseudopotential calculations which have been observed to overestimate momentum density between 0 and 1.5?a.u., while the reverse trend is seen above 1.5?a.u. We thus conclude that improvement to the pseudopotential technique to obtain the Compton profile is possible if the sharp Fermi break of the momentum distribution between high and low momenta becomes more smeared. Using the broadened spectral functions via the contour deformation method to obtain the momentum distributions, the GWA is a natural tool to achieve this via the contribution from the dielectric screening to the quasiparticle energies.