Structural, elastic, vibrational and electronic properties of amorphous Al2O3 from ab initio calculations

Abstract

First-principles molecular dynamics calculations of the structural, elastic, vibrational and electronic properties of amorphous Al2O3, in a system consisting of a supercell of 80 atoms, are reported. A detailed analysis of the interatomic correlations allows us to conclude that the short-range order is mainly composed of AlO4 tetrahedra, but, in contrast with previous results, also an important number of AlO6 octahedra and AlO5 units are present. The vibrational density of states presents two frequency bands, related to bond-bending and bond-stretching modes. It also shows other recognizable features present in similar amorphous oxides. We also present the calculation of elastic properties (bulk modulus and shear modulus). The calculated electronic structure of the material, including total and partial electronic density of states, charge distribution, electron localization function and the ionicity for each species, gives evidence of correlation between the ionicity and the coordination for each Al atom.