Geometric, Electronic, and Magnetic Properties of MgH2: Influence of Charged Defects

A study on the effect of the presence of charged vacancy on the electronic and magnetic properties of perfect magnesium hydride is presented. To this aim spin polarized ab initio calculations for the MgH2 structure containing a H vacancy or a Mg vacancy or a H–Mg divacancy were used. For each case three possible charge states (q = +1, 0, and −1) were taken into account. The calculated parameters were the vacancy formation energy, band gap, magnetic moment, Fermi level position with respect to the top of the valence band, and the bottom of the conduction band and density of states curves. From the calculations, it was found that positive and negative charged H vacancies and the negative charged divacancy are the most probable formed defects. Besides, the presence of a negative or neutral H vacancy produces an important reduction of the band gap, which should improve the semiconductor behavior of the material. Furthermore, the charged H vacancies provoke an important local rearrangement in the structure of the hydride. However, the positive charged Mg vacancy induces the highest magnetic moment.