Electronic and Structural Properties of Bulk γ‐Al 2 O 3

γ‐Al 2 O 3 is a defective spinel phase of alumina with cation site vacancies randomly distributed. Its structure and properties are not well understood. There has been long‐standing controversy as to whether the cation vacancies are located at the tetrahedral sites or the octahedral sites. Based on an empirical pair potential calculation and first‐principles electronic structure studies, we have concluded that cation vacancies are preferentially located at the octahedral sites in bulk γ‐Al 2 O 3 . Our calculation shows that the electronic structure of γ‐Al 2 O 3 differs from that of α‐Al 2 O 3 in fine details. γ‐Al 2 O 3 has a smaller band gap and wider valence bandwidths. The calculated density of states (DOS) of γ‐Al 2 O 3 is in good agreement with recent experimental XPS and XES data. Site‐ and orbital‐resolved partial DOS (PDOS) of Al atoms shows significant dependence on the local coordinations. The PDOS of an oxygen adjacent to a vacancy differs substantially from that of a fully coordinated anion.