Computational Analysis of Physical Properties and Hydrogen Storage Mechanism of X 2 AlH 6 (X = Ca, Sr, and Ba) Hydrides for Hydrogen Storage Applications

ABSTRACT The structural and physical properties of double perovskite hydrides X 2 AlH 6 (X = Ca, Sr, and Ba) have been researched for the first time using first‐principles methods. The calculated formation energies, elastic constants, and phonon dispersion curve of X 2 AlH 6 indicate that these compounds are thermodynamically, mechanically, and dynamically stable, making them synthesizable. Based on Poisson's ratio and B/G, Sr 2 AlH 6 and Ba 2 AlH 6 both exhibit good ductility, while Ca 2 AlH 6 is classified as brittle. Furthermore, the electronic properties show that all X 2 AlH 6 compounds exhibit metallic characteristics. The analysis of optical properties shows that Ca 2 AlH 6 has the highest dielectric constant and refractive index, making it particularly suitable for hydrogen storage materials and infrared waveguides. The calculated gravimetric hydrogen storage capacities (GHSC) of Ca 2 AlH 6 , Sr 2 AlH 6 , and Ba 2 AlH 6 are 5.343, 2.904, and 1.966 wt%, respectively, and their desorption temperatures are 257.738, 279.503, and 245.807 K, respectively. Overall, this research provides valuable insights into the potential applications of aluminum‐based hydrides in next‐generation hydrogen storage technology.