Effects of Native Vacancies on Nb-Doped MgH₂ Using Density Functional Theory Calculations

Abstract

In the present work we considered the effect of Nb and charged vacancies in the properties of magnesium hydride. We performed spin polarized ab initio calculations substituting a Mg atom by a Nb impurity. Then some charged vacancies were included in the MgH 2 +Nb system (V H , V Mg or V Mg-H). In each case three possible charge states were considered (+1, 0 or-1). We computed cohesion and formation energy, bandgap and magnetic moment. We also calculate the transition level energy value and the density of states. Nb states are located in the gap, and a magnetic moment is induced. In the case of the system with charged vacancies we found that the V H + and V H 0 are the more probable formed and the states near the Fermi level (E F) are filled thus getting an important reduction in the bandgap.