Ab Initio Computational Studies of Mg Vacancy Diffusion in Doped MgB₂Aimed at Hydriding Kinetics Enhancement of the LiBH₄+ MgH₂System

We report an ab initio density functional theory (DFT) study that investigates the effect of transition metal dopants on diffusion of Mg vacancies in MgB 2 . This study has implications for the diffusion-controlled hydriding kinetics of the technologically important LiBH 4 + MgH 2 hydrogen storage system. The first-principles calculation reveals that the solubility of M (M = Ni, Mn, V, Ti, Sc, and Y) in MgB 2 and the migration barriers of Mg vacancies are dictated by the dopant’s atomic radius, whereas the formation energies of Mg vacancies are strongly affected by both the dopant’s atomic radius and charge distribution. Mn, Sc, and Y are found to have the potential to enhance the diffusion rate of Mg, whereas V and Ti are poor dopants in enhancing the diffusion rate of Mg in MgB 2 . The findings in this study are consistent with existing experimental results.