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

We selected two important γ-alumina models proposed in literature, a spinel-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 spinel-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. -- Graphical abstract: Two γ-Alumina bulk models selected in this work for a comparison focusing in the electronic structure and thermodynamics of the systems. (a) The nonspinel model and (b) the spinel-like model. Display Omitted Highlights: → There is still a debate about the γ-Alumina structure in the literature. → Models of surfaces are constructed from different bulk structural models. → Two models commonly used in the literate were selected and compared. → One model reproduce better the experimental data. → Both presented a similar electronic structure.