Hydrogen Storage Performance of XBeH3 (X = Mg, Ca, Sr) Hydrides: Insights From DFT and AIMD Simulations

Abstract

Hydrogen storage remains a key challenge for the development of clean and sustainable energy technologies. In this work, the structural stability, electronic behavior, thermodynamic properties, and hydrogen storage performance of cubic ${\mathrm{XBeH}}_3$ hydrides, where X = Mg, Ca, and Sr, are investigated using first-principles calculations and ab initio molecular dynamics simulations. The optimized structures show negative formation energies, while phonon dispersion calculations confirm the dynamical stability of all three compounds. The thermal behavior was further examined by AIMD simulations, which show no structural degradation at 300 K. The electronic calculations reveal that all three compounds are metallic, a feature that could facilitate electronic charge redistribution during hydrogen absorption and desorption. ${\mathrm{MgBeH}}_3$, ${\mathrm{CaBeH}}_3$, and ${\mathrm{SrBeH}}_3$ exhibit gravimetric hydrogen capacities of 8.32, 5.80, and 3.03 wt%, respectively. The estimated desorption temperatures are 516.75 K for ${\mathrm{MgBeH}}_3$, 376.40 K for ${\mathrm{CaBeH}}_3$, and 258.37 K for ${\mathrm{SrBeH}}_3$. On this basis, ${\mathrm{MgBeH}}_3$ stands out as the most promising member of the series, although the other two compounds also provide useful insight into the effect of alkaline-earth substitution. These results provide a useful theoretical starting point for future studies on Be-containing perovskite hydrides.