Computational strategy to explore AlMgX₃ (X = F, Cl, Br, I, H) perovskites for energy applications

The growing demand for clean energy and the limits of fossil-fuel hydrogen require stable, tunable materials for photocatalytic water splitting and solid-state hydrogen storage. First-principles study of AlMgX₃ (X = F, Cl, Br, I, H) covering structural, mechanical, electronic, optical, phonon, thermodynamic, photocatalytic, and hydrogen storage properties. All compounds stabilize in the cubic Pm-3m phase; formation energies confirm stability. Elastic constants satisfy Born–Huang criteria; AlMgCl₃, AlMgBr₃, and AlMgI₃ are ductile, while AlMgF₃ and AlMgH₃ are brittle. Electronic results: GGA-PBE band gaps 1.208–3.180 eV, increasing to 2.174–4.082 eV with HSE06; AlMgH₃ remains metallic. DOS/PDOS show p-state dominance near halide band edges. Optical spectra exhibit strong UV–visible absorption and high dielectric response. Phonon and thermodynamic analysis confirm phase stability. AlMgCl₃ and AlMgBr₃ straddle redox levels, enabling UV water splitting; AlMgH₃ shows 5.57 wt% H₂ storage. AlMgX₃ perovskites are promising for energy applications.