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The ionization potential(IP)is the key to determine valence and conduction band edges of a semiconductor with respect to the vacuum level,which play a crucial role in physical and chemical properties of surfaces and interfaces.In this work,a set of prototypical semiconductors are considered to establish the performance of the first-principles approaches to calculate IPs of solids[1].We have shown that in general Kohn-Sham density functional theory with local density approximation or generalized gradient approximation(LDA/GGA)significantly underestimates the IPs of typical semiconductors.In contrast,much better agreement between theory and experiment can be obtained when we take into account the GW quasi-particle correction implemented in the linearized augmented planewaves(LAPW)basis[2].We have made a critical comparison between two GW correction schemes,one considering the GW correction to the valence band maximum(VBM)of bulk systems,and the other assuming that the LDA/GGA gives correct band gap center(BGC).Our study shows that the VBM scheme is theoretically better founded and practically leads to closer agreement with experiment than the BGC scheme.We also investigated the performance of the hybrid functionals and we found that the popular hybrid functionals like HSE06 can also give much more accurate description of IPs than LDA/GGA,but they exhibit more significant errors for systems with stronger ionic characters.