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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.
