First-Principles Calculation of the Crystal Structure and Stabilization of Mg-Ti-H System

Abstract

First-principles calculations were performed to determine the equilibrium crystal structures, energetic properties, and stability of MgxTi(1-x)H2 (x=0.25, 0.5, 0.75, 0.875) systems containing different amounts of titanium using the pseudopotential plane-wave method based on density functional theory. The calculation results show that the hydrogen atoms in the MgxTi(1-x)H2 hydrides roughly occupy the tetrahedral interstitial sites. The calculated H-Ti distances are less than the H-Mg distances. This indicates that Ti has a more notable affinity for hydrogen than Mg. The bonding strength of H-Mg is weaker when the Ti atom attracts surrounding hydrogen atoms. The stabilization and dehydrogenation temperatures of the hydrides MgxTi(1-x)H2 are lower than those of MgH2 with an increasing Ti content. This indicates that titanium can reduce the decomposition temperature of the MgxTi(1-x)H2 hydrides and play a significant catalytic role in improving the dehydrogenation dynamic properties of the MgxTi(1-x)H2 hydrides.