Theoretical investigation of XSnH3 (X: Rb, Cs, and Fr) perovskite hydrides for hydrogen storage application

The current study investigated the structural, mechanical, electronic, and optical properties of new perovskite hydrides XSnH3 (X = Rb, Cs, and Fr) for hydrogen storage applications using a first-principles study with the GGA-PBE approach. The calculated lattice constants form optimized cubic crystal have 4.40 & Aring;, 4.49 & Aring; and 4.53 & Aring; for RbSnH3, CsSnH3, and FrSnH3 hydrides, respectively. These materials were found to be thermodynamically and mechanically stable structures owing to their negative cohesive energy and elastic constants. Additionally, molecular dynamics (MD) calculations were performed to study the thermal stability of the current materials. These results indicate that the considered materials were stable and exhibited no structural deformation. The electronic band structure and density of states confirmed that the current materials exhibit metallic behavior via overlapping of the valence and conduction bands with a zero-energy band gap. It was found these compounds have anisotropic and rigid in nature. The Poisson's ratio, Pugh's ratio (B/G), and Cauchy pressure (CP) values indicate that the current compounds have ionic bonding and brittle behavior. Different optical parameters were calculated for these materials, such as the conductivity, dielectric function, loss energy, refractive index, and adsorption. Interestingly, these optical parameters indicate that XSnH3 is promising for optoelectronic, photonic, and energy storage applications. Finally, the calculated hydrogen storage capacities for RbSnH3, CsSnH3, and FrSnH3 are 1.45 wt%, 1.18 wt %, and 0.87 wt %respectively. These results show that current materials have the potential and promise for hydrogen storage applications, and devices.