The structure of γ-Al2O3, a crucial catalyst support, remains debated, particularly the Al³⁺ cation and vacancy locations.  While models propose spinel and non-spinel structures, NMR and DFT data support a predominantly spinel structure (62.5-65% octahedral Al³⁺), contradicting non-spinel models.  TEM reveals significant γ-Al2O3 surface reconstruction, with (111) facets favored over atomically flat (110) surfaces.  The non-spinel model requires reevaluation.