Investigation of Hydrogen Storage Capacity and Physical Aspects of XCa 3 H 9 (X = P, As, Sb) Hydrides: A DFT Insight

ABSTRACT The current work presents the structural, optoelectronic, hydrogen (H 2 ) storage, and mechanical features of novel cubic hydrides XCa 3 H 9 (X = P, As, Sb). The negative formation energies and AIMD simulations confirm that the studied materials are thermodynamically stable. The materials demonstrate gravimetric storage capacities ( C wt% ) of PCa 3 H 9 (5.66 wt%), AsCa 3 H 9 (4.44 wt%), and SbCa 3 H 9 (3.61 wt%), suggesting higher capacity for PCa 3 H 9 exceeding DOE's goal of 5.5 wt%. Additionally, PCa 3 H 9 demonstrates the highest volumetric capacity of 109.1 g.H 2 /L compared to AsCa 3 H 9 (106 g.H 2 /L) and SbCa 3 H 9 (98.4 g.H 2 /L). The desorption temperatures are 348.8, 319.1, and 333.9 K for PCa 3 H 9 , AsCa 3 H 9 , and SbCa 3 H 9 , respectively. Mechanical evaluations have been performed to analyze the ductility or brittleness, melting points, Debye temperature, and phase stability under stress. Electronic band structures of XCa 3 H 9 (X = P, As, Sb) validate the metallic nature of PCa 3 H 9 , which varies to semiconductor characteristics for AsCa 3 H 9 and SbCa 3 H 9 , with indirect narrow band gaps of 0.28 and 0.88 eV according to Tran–Blaha‐modified Becke–Johnson (TB‐mBJ) calculations. The optical characteristics offer insights into absorption, energy dissipation, light transmission, and reflection, suggesting optoelectronic potential. These perovskite hydrides have elevated absorption coefficients (∼10 5 cm −1 ), indicating their potential for energy harvesting applications. Collectively, the analyzed results emphasize that PCa 3 H 9 is a more beneficial material for applications involving H 2 storage.