First principles study of double perovskite X2MgH6 (X = Li, Na) hydrides for hydrogen storage applications

초록

The double-perovskite X2MgH6 hydrides (X = Li and Na) are investigated using first-principles calculations to explore their structural, mechanical, optoelectronic, and thermoelectric properties for energy-conversion applications. The Generalized Gradient Approximation-Perdew Burke Ernzerhof functional implemented in the Vienna Ab Initio Simulation Package is employed to optimize the structural and mechanical behaviour of the hydrides. The Born stability criteria confirm the mechanical stability, and the electronic properties reveal metallic behavior. Optical analysis indicates strong photon-material interactions, reflected by high refractive indices (8.32 for Li2MgH6 and 8.89 for Na2MgH6), with Na2MgH6 showing enhanced optical response. Thermoelectric properties demonstrate favorable transport performance and stability. The hydrogen storage capacities are calculated to be 13.68 wt% for Li2MgH6 and 7.93 wt% for Na2MgH6. The combined mechanical, electronic, optical, and thermoelectric properties suggest that X2MgH6 hydrides are promising candidates for energy conversion and hydrogen storage applications.

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