First-principles study on structural stability of 3d transition metal alloying magnesium hydride

Abstract A first-principles plane-wave pseudopotential method based on the density functional theory was used to investigate the energy and electronic structure of magnesium hydride (MgH 2 A) alloyed by 3d transition metal elements. Through calculations of the negative heat formation of magnesium hydride alloyed by X (X denotes 3d transition metal) element, it is found that when a little X (not including Sc) dissolves into magnesium hydride, the structural stability of alloying systems decreases, which indicates that the dehydrogenation properties of MgH 2 can be improved. After comparing the densities of states(DOS) and the charge distribution of MgH 2 with or without X alloying, it is found that the improvement for the dehydrogenation properties of MgH 2 alloyed by X attributes to the fact that the weakened bonding between magnesium and hydrogen is caused by the stronger interactions between X (not including Cu) and hydrogen. The calculation results of the improvement for the dehydrogenation properties of MgH 2 -X (X=Ti, V, Mn, Fe, Co, Ni, Cu) systems are in agreement with the experimental results. Hence, the dehydrogenation properties of MgH 2 are expected to be improved by addition of Cr, Zn alloying elements.