Tuning the structural, optoelectronic, mechanical, and hydrogen storage properties of metal hydride RbGeCl ₃ : DFT insight

This work analyzed the impact of hydrogenation on the structural, mechanical, optoelectronic, and hydrogen storage properties of cubic RbGeCl 3 using density functional theory with the generalized gradient approximation PBE functional. As hydrogen is incorporated, the pristine direct band gap of 1.02 eV is systematically reduced, resulting in the material transitioning from an indirect band gap to a metallic one. Based on the negative formation energies, hydrogenated systems are stable and potentially synthesizable. The mechanical properties, including bulk modulus, shear modulus, and Young’s modulus, exhibited nonlinear behaviour with increasing hydrogen concentration. A nonlinear variation in mechanical properties is observed, with optimal performance at x = 0.6. Hydrogen storage parameters, such as gravimetric capacity and desorption temperature, are calculated to assess the material’s likelihood for hydrogen storage applications. The value of gravimetric capacity (0.89 cw%) with lower desorption temperature suggests that RbGeCl 1.2 H 1.8 is a suitable candidate for solid-state hydrogen storage applications. As a whole, RbGeCl 3- x H x exhibits tunable multifunctional properties that are suitable for applications in the advanced energy and electronic sectors.