Tetragonal structure model for boehmite-derived γ-alumina

γ-alumina (γ-Al 2 O 3 ) derived from boehmite has historically been described as having a cubic spinel structure with Fd3m symmetry, despite reports of tetragonal distortion in the structure. Based on neutron diffraction, transmission electron microscopy, and magic angle spinning NMR data, we propose a tetragonal model for the structure of boehmite-derived γ-Al 2 O 3 with 14 1 /amd space group symmetry, a maximal subgroup of Fd3m. It is also demonstrated that an accurate average structural model cannot be achieved if the cations are restricted to spinel positions.