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The current study investigated the structural, mechanical, electronic, and optical properties of new perovskite hydrides XSnH 3 (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 Å, 4.49 Å and 4.53 Å for RbSnH 3 , CsSnH 3 , and FrSnH 3 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 (C P) 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 XSnH 3 is promising for optoelectronic, photonic, and energy storage applications. Finally, the calculated hydrogen storage capacities for RbSnH 3, CsSnH 3, and FrSnH 3 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. [Display omitted] • Three novel perovskite hydrides are examined for hydrogen storage using DFT. • XSnH 3 (X = Rb, Cs, and Fr) hydrides are mechanically and thermodynamically stable. • XSnH 3 perovskites are metallic in nature. • Hydrogen storage capacities of XSnH 3 (X = Rb, Cs, and Fr) hydrides are 1.45 wt%, 1.18 wt %, and 0.87 wt %respectively. [ABSTRACT FROM AUTHOR]

The present study utilizes First-principles calculations to investigate the physical properties of Mn-based perovskite-type hydrides XMnH 3 (X = K, Li) including electronic, magnetic, and optical properties. The lattice parameters are calculated as 3.69 and 3.29 Å for KMnH 3 and LiMnH 3 , respectively. The electronic and magnetic properties of both materials indicate that they are metallic and have ferromagnetic nature. The charge density, electron density and population analysis also have been analyzed to get an in-depth information about the structures of the studied materials. The reflectivity shows that both materials have a reflective surface due to the metallic nature. Both of the materials are found to be highly transparent and capable of accommodating polarization inside them. KMnH 3 is found to be more interactive with the incident photons and has a greater ability for polarization and storing the incident electromagnetic radiations. The optical conductivity described the conduction mechanism inside the materials. It is revealed that LiMnH 3 has a very low energy loss than KMnH 3 in the lower energy regime. Additionally, the hydrogen storage capability of Mn-based perovskite-type hydrides is briefly studied. The gravimetric hydrogen storage capacity is found to be 3.12 and 4.67 wt% for KMnH 3 and LiMnH 3 , respectively. The lower energy loss and higher gravimetric hydrogen storage capacity in LiMnH 3 suggest that it is a superior option for hydrogen storage applications. • The physical properties of KMnH 3 and LiMnH 3 are investigated by using CASTEP code. • Both the materials have zero band gap and possess metallic nature. • LiMnH 3 is suggested as a preferred material for hydrogen storage application. [ABSTRACT FROM AUTHOR]