Stability and mobility of native point defects in AlH3

We investigate the properties of native point defects in AlH3 using density functional theory (DFT). The results indicate that mass transport in AlH3 is mediated by positively charged hydrogen vacancies (VH+), with an activation energy of 1.72 eV that is in good agreement with experimentally observed values for the dehydrogenation of AlH3. An accurate description of the point-defect properties requires use of an advanced hybrid DFT/Hartree–Fock approach with the functional of Heyd, Scuseria, and Enzerhof (HSE), as revealed by a detailed comparison with results obtained using a conventional generalized gradient approximation functional. The HSE produces a more accurate band gap, and significant differences are found for the formation energies of the defects between HSE and PBE. We discuss the differences in terms of an alignment of the band structures and defect transition levels on an absolute energy scale.