DFT study of hydrogen absorption in high-pressure tetragonal phase of Mg3LaHn with Y and Sc additions

The pseudo-potential Density Functional Theory (DFT) method using the Generalized Gradient Approximation (GGA) is applied to investigate hydrogen insertion trends in Mg3La alloy in several high-pressure tetragonal phases. The addition effect of Y and Sc on the stability, structural properties and hydrogen interaction energies of Mg3La and its hydrides are investigated. The main results indicate that stability of the Mg3La alloy is increased by hydrogen insertion. The high-pressure tetragonal structure with space group (P4/mmm) is the most stable structure of Mg3LaH9 hydride in agreement with the available PCI curve of Mg3LaHn alloy. Systems with Sc and Y additions are characterized by the weakest interaction energy values, which would be better for kinetics consideration. The Molecular Dynamic (MD) calculations are applied to investigate the temperature effects on the diffusion coefficient of the hydrogen atoms. The results confirm that the hydrogen diffusion is responsible for the phase transitions observed in these systems with increasing temperature.