Indium-oxide polymorphs from first principles: Quasiparticle electronic states

The electronic structure of In₂O₃ polymorphs is calculated from first principles using density functional theory (DFT) and many-body perturbation theory (MBPT). DFT calculations with a local exchange-correlation (XC) functional give the relaxed atomic coordinates of the two stable polymorphs. Their electronic structure, i. e. , the band structure and density of states, is studied within MBPT. The quasiparticle equation is solved in two steps. As the zeroth approximation for the XC self-energy the nonlocal potential resulting from a HSE03 hybrid functional is used. In the sense of a self-consistent procedure G₀W₀ quasiparticle corrections are computed on top. The calculated direct quasiparticle gaps at amount to 3. 30. 3em{0ex}eV (rhombohedral) and 3. 10. 3em{0ex}eV (cubic). The rhombohedral polymorph is found to exhibit a near degeneracy of the valence-band maxima at the point and on the -L line, while the valence-band maximum of the cubic polymorph occurs near. Interconduction band transitions are identified as possible origin of conflicting experimental reports, claiming a much larger difference between the direct and indirect gap. The results for gaps, d-band positions, and density of states are compared with available experimental data.