A DFT investigation of Sc-based perovskite-type hydrides XScH3 (X = K, Na) for hydrogen storage application

The current study delves into the physical properties and hydrogen storage capabilities of XScH₃ (X = K, Na) using the CASTEP code by leveraging the GGA-PBE method. The examined values of the lattice constants for KScH₃ and NaScH₃, are 4.19 and 4.07 Å, respectively. With a zero band gap revealing the metallic behavior, both compounds are discovered to be mechanically and thermodynamically stable in the cubic phase. Both compounds exhibit substantially enhanced conductivity and absorption in the low-energy range. While comparing NaScH₃ to KScH₃, the reflectivity and refractive index values for the former are significantly higher. Both the materials possess anisotropic and hard nature represented by anisotropic factor, young’s modulus, bulk modulus and mean shear modulus. Both compounds exhibit the brittle nature which is investigated with the help of poisson ratio and Pugh’s ratio. The values of bulk modulus, young’s modulus and mean shear modulus are higher for KScH₃ than NaScH₃ showing more hardness in KScH₃. The ratio of gravimetric hydrogen storage is found 3.48 and 4.27 wt %, for KScH₃ and NaScH₃, respectively which shows that both materials can accommodate a good amount of hydrogen, however, NaScH₃ can be preferred for hydrogen storage applications due to the higher storage capacity of hydrogen.