Hydrogen storage potential of cubic InXH₃ (X = Be, Mg, Ca, Sr, Ba, Ra) hydride perovskites: a comprehensive first principles investigation

Safe and efficient solid state hydrogen storage remains a major challenge for practical hydrogen energy systems, particularly in achieving thermodynamic stability with favorable release characteristics. In this work, the hydrogen storage potential of cubic hydride perovskites InXH₃ (X = Be, Mg, Ca, Sr, Ba, Ra) is systematically investigated using density functional theory within the CASTEP framework. Structural optimization confirms stabilization in the cubic Pm-3 m phase with tolerance factors ranging from 0.8450 to 1.0884, indicating geometric suitability for hydrogen incorporation. Elastic constants satisfy mechanical stability criteria, and bulk modulus decreases from 25.55 GPa for InMgH3 to 14.09 GPa for InRaH3, revealing tunable lattice stiffness that can influence hydrogen release behavior. Electronic structure analysis shows metallic character for InBeH₃ and InMgH₃, while InCaH₃, InSrH₃, and InBaH₃ exhibit direct band gap semiconducting nature with HSE06 band gaps of 0.574 eV, 0.496 eV, and 1.045 eV, supporting stable bonding environments. Optical response across 0–35 eV confirms robust dielectric and absorption characteristics. All compounds possess negative formation energies, confirming thermodynamic feasibility. InBeH₃ exhibits the highest gravimetric capacity of 2.38 wt% and volumetric capacity of 57.15gH₂/L. Estimated desorption temperatures for all hydrides exceed room temperature and increase with atomic mass, indicating controlled hydrogen release suitable for off board hydrogen storage applications.