Efficient double perovskite hydrides A ₂ AlXH ₆ (A=Li, Na; X= Ga, In) for advanced hydrogen storage applications: First-principles investigation

The solid-state hydrogen storage (SSHS) technologies based on perovskite hydrides are more effective and convenient substitutes to liquefied hydrogen (H 2 ), with more storage capability and a suitable desorption temperature. The present research examines the elastic, thermodynamic, storage density, desorption temperature, and electro-optic traits of double perovskite hydrides (DPHs) A 2 AlXH 6 (A=Li, Na; X=Ga, In), utilizing the WIEN2k package. The structural optimization confirms phase stability, while the formation energy indicates thermal robustness and the possibility of synthesis. The H 2 storage attributes are investigated, and the results show the gravimetric capacities of Li 2 AlGaH 6 (5.19 wt%), Na 2 AlGaH 6 (4.07 wt%), Na 2 AlInH 6 (3.91 wt%), and Li 2 AlInH 6 (3.24 wt%). The calculated desorption temperatures are 307.8 K for Li 2 AlGaH 6 , 317.9 K for Na 2 AlGaH 6 , 295.8 K for Na 2 AlInH 6 , and 320.4 K for Li 2 AlInH 6 , and are also in the most favourable desired range for desorption temperature (233-333 K). The elastic aspects are estimated to demonstrate stability, brittleness, and anisotropy. Furthermore, thermodynamic metrics are assessed utilizing the mechanical characteristics, which affirm the stability against thermal vibrations. The patterns of electronic bands and density of states calculated using TB-mBJ potentials show the presence of metallic behavior. The findings confirm that A 2 AlXH 6 perovskite hydrides are adjustable in functionality and have a promising future in developing SSHS technologies.