Electronic properties of bulkγ−Al2O3

The electronic structure of bulk $\ensuremath{\gamma}$-alumina is investigated using Density Functional Theory. Recent theoretical structures, including occupation of nonspinel positions, are used as starting point for energy minimization, allowing for relaxation of the cell shape and the ionic positions. A comparison of simulated diffraction patterns of the present and recent theoretical and experimental structural models is presented. The electronic structure is described in terms of band structure, density of states, charge density, electron localization function, and ionic charges. The valence band density of states of $\ensuremath{\gamma}$-alumina is similar to $\ensuremath{\alpha}$- and $\ensuremath{\kappa}$-alumina, although a smaller bandgap is found. It is shown that $\ensuremath{\gamma}$-alumina ionicity is similar to other alumina phases, with a high localization of the electrons at oxygen atoms. The smaller bandgap of $\ensuremath{\gamma}$-alumina is attributed to the structural disorder.