Direct comparison between two γ-alumina structural models by DFT calculations

We selected two important gamma-alumina models proposed in literature, a spinet-like one and a nonspinel one, to perform a theoretical comparison. Using ab initio calculations, the models were compared regarding their thermodynamic stability, lattice vibrational modes, and bulk electronic properties. The spinel-like model is thermodynamically more stable by 4.55 kcal/mol per formula unit on average from 0 to 1000 K. The main difference between the models is in their simulated infrared spectra, with the spinet-like model showing the best agreement with experimental data. Analysis of the electronic density of states and charge transfer between atoms reveal the similarity on the electronic structure of the two models, despite some minor differences. (C) 2011 Elsevier Inc. All rights reserved.