Effect of semicore orbitals on the electronic band gaps of Si, Ge, and GaAs within the GW approximation

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Abstract
We study the effect of semicore states on the self-energy corrections and electronic energy gaps of Si, Ge, and GaAs. Self-energy effects are computed within the GW approach, and electronic states are expanded in a plane-wave basis. For these materials, we generate ab initio pseudopotentials treating as valence states the outermost two shells of atomic orbitals, rather than only the outermost valence shell as in traditional pseudopotential calculations. The resulting direct and indirect energy gaps are compared with experimental measurements and with previous calculations based on pseudopotential and “all-electron” approaches. Our results show that, contrary to recent claims, self-energy effects due to semicore states on the band gaps can be well accounted for in the standard valence-only pseudopotential formalism.
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