Distribution of tetrahedral and octahedral Al sites in gamma alumina

Experimental and computational studies of gamma-Al2O3 show that 70 +/- 2% of Al ions occupy octahedral interstitial sites in the fcc oxygen structure, and the rest tetrahedral sites. The experimental data come from Al-27 MAS NMR and the theoretical results from ab initio quantum mechanical energy calculations for nine superlattice structures, analysed to extract various parameters which were then fed into a Monte Carlo simulation of the gamma-Al2O3 structure. The simulation throws new light on the reasons for the structural disorder.