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ABSTRACT Solid‐state hydrogen storage materials must simultaneously deliver high hydrogen capacity, favorable thermodynamics, and robust structural stability—criteria that remain difficult to achieve in a single material system. Vacancy‐ordered double perovskite hydrides Li 2 MH 6 (M = Si, Ge, Ti, Zn) represent an emerging and largely unexplored class with potential to overcome these limitations. Here, we employ first‐principles density functional theory using GGA‐WC and HSE06 functionals to systematically investigate their structural, mechanical, electronic, vibrational, and hydrogen storage properties. All compounds are found to be thermodynamically stable, with formation enthalpies ranging from −15.67 to −19.42 kJ mol −1 H 2 and dynamically stable, as confirmed by phonon spectra free of imaginary modes. Mechanical stability is ensured by elastic constants satisfying Born criteria, with bulk moduli of 28–46 GPa. Hybrid functional calculations reveal indirect band gaps of 2.20–2.26 eV for Li 2 SiH 6 , Li 2 GeH 6 , and Li 2 TiH 6 , while Li 2 ZnH 6 exhibits near‐metallic behavior. Remarkably, these hydrides deliver high gravimetric hydrogen capacities of 6.48–11.43 wt% and practical desorption temperatures between 334 and 378 K, exceeding the DOE 2025 targets. These results identify Li 2 MH 6 hydrides as a promising, tunable platform for next‐generation hydrogen storage and energy applications.
Goutni et al. (Tue,) studied this question.