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Abstract

Focusing on the fundamental band gaps in Si, diamond, BN, LiF, AlP, NaCl, CaSe and GaAs, and the semicore d-state binding energies in ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe and GaN, we study the differences between the all-electron (AE) G₀W₀G0W0 method. Leaving aside issues related to the choice of PPs within PP-G₀W₀, we analyze in detail the well-known discrepancies between AE-G₀W₀ and PP-G₀W₀ band gaps by separately addressing the approximations underlying PP-G₀W₀, i.e. the frozen-core approximation, the core–valence partitioning and the use of pseudo-wavefunctions. The largest differences, of the order of eV, appear in the exchange part of the self-energy and the exchange–correlation potential due to the core–valence partitioning. These differences cancel each other and, in doing so, make the final core–valence partitioning effect on the band gaps controllable when the semicore states are treated as valence states. This cancelation, however, is incomplete for semicore d-state binding energies, due to the strong interaction between these semicore states and the deep core. From our comprehensive analysis, we conclude that reliably describing the many-body interactions at the G₀W₀ level and providing benchmark results require an AE treatment.