Statistics-Based Analysis of the Evolution of Structural and Electronic Properties of Realistic Amorphous Alumina During the Densification Process: Insights from First-Principles Approach

On the basis of the melt and quench strategy, over 3000 structurally different AlOx structures have been generated using ab initio molecular dynamics. Unlike other previous studies where defects were introduced into some crystalline polymorph of Al2O3, a variety of defects emerged directly from this approach. A new way to probe the short (distances between first neighbors and coordination numbers) and medium (atom rings, bond angles, and distances between second neighbors) range structural properties of H- and/or O-rich AlOx has been defined. The evolution of such structural properties during the densification process with mass loss has been studied using averaged data at a fixed chemical composition. A good agreement is observed between experimental and theoretical structural data, validating the methodology. In particular, the profile of the total experimental neutron pair correlation function has been rationalized. At fixed composition, the Spearman correlations have been calculated in order to reveal monotonic relationships between properties: a correlation between the structure and band gap energy of different stoichiometries of AlOx could not be clearly inferred. Finally, we may speculate that the O-2(2-) and Al-H defects could explain the origin of negative fixed charges in AlOx because of their effects on electronic properties of AlOx and their structural characteristics.