Computational assessment of MgXH3 (X = Al, Sc and Zr) hydrides materials for hydrogen storage applications

This manuscript reports the computational study of three new perovskite-type hydrides for solid-state hydrogen storage technology. Herein, Density Functional Theory (DFT) has been implemented within CASTEP code to probe the structural, electronic, mechanical, optical and hydrogen storage properties of MgXH3 (X = Al, Sc and Zr). Thermodynamic stability assessments reveal that all materials exhibit negative formation energy (ΔEf), guaranteeing their energetic stability and suitability for experimental synthesis. Band structure and density of states plots highlight metallic properties in MgXH3 hydrides. The mechanical stability of these perovskites was ensured by the compliance of their elastic constants with Born's stability criteria. Bulk modulus, shear modulus, Poisson's ratio, Cauchy pressure, etc. are also processed from elastic constants. Pugh coefficient and Cauchy pressure unveil ductile behavior in MgAlH3 and MgZrH3, and brittleness in MgScH3. Optical properties revealed that MgXH3 compounds have maximum absorption and conductivity in the ultraviolet region. The gravimetric hydrogen storage capacities were theoretically determined as 5.274, 4.015, and 2.487 wt%, for MgAlH3, MgScH3, and MgZrH3 respectively. This research work suggests that MgXH3 (X = Al, Sc and Zr) can be used as promising materials for hydrogen storage applications.