Structural, mechanical, electronic, optical, gravimetric, and thermodynamic properties of AYH3 (A = K, Rb) compounds: A DFT study

This work presents a comprehensive density functional theory (DFT) investigation of Yttrium-based perovskite hydrides AYH 3 (A = K, Rb) for solid-state hydrogen storage. First-principles calculations confirm both compounds crystallize in cubic structures and exhibit thermodynamic stability, evidenced by negative formation energies of −0.458 eV/atom for KYH 3 and −0.437 eV/atom for RbYH 3 . Hydrogen storage evaluation reveals KYH 3 achieves a superior gravimetric capacity of 2.31 wt% compared to 1.70 wt% for RbYH 3 , with desorption temperatures of 338 K and 323 K respectively. Electronic structure analysis using both GGA-PBE and HSE06 functionals confirms metallic behavior for both materials, which could promote favorable charge-carrier mobility for storage applications. Mechanical property assessment indicates brittle characteristics with Pugh's ratios below 1.75. The comprehensive analysis identifies KYH 3 as the more promising candidate, combining enhanced hydrogen storage capacity with practical thermal properties for potential application in hydrogen storage systems. • The physical properties of AYH 3 (A = K, Rb) compounds have been investigated. • The AYH 3 hydrides are both thermodynamically and mechanically stable and can be synthesized. • The electronic structures of KXH₃ compounds confirm their metallic nature. • The optical properties of KXH 3 perovskites (X = Zn, and Hf) are analyzed using a (DFT) approach.