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

Abstract

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 2A) 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.