Computational study to investigate effectiveness of titanium substitution in CaFeH3 perovskite-type hydride: An approach towards advanced hydrogen storage system

In recent years, there has been increased interest in hydrogen storage due to the numerous advantages hydrogen offers as an energy source. This study explores the structural, hydrogen storage, electronic, elastic, mechanical, and optical properties of Ca1-xTixFeH3 through DFT. After Ti substitution in the host material, structure phase transformation occurs: cubic → pseudo-cubic → cubic. Study compounds are thermodynamically stable and experimentally synthesizable according to the calculated negative formation energies. Gravimetric hydrogen storage capacities for different concentrations of Ti (x = 0, 0.11, 0.33, 0.55, 1) were calculated as 2.963, 2.938, 2.843, and 2.753 wt%, respectively. The investigation focuses on understanding the material's BS, Fermi level, and DOS, elucidating its metallic characteristics, and non-zero DOS at the Fermi level contributing to electrical and thermal conductivity. Elemental partial density of states reveals hybridization effects with Ti doping, affecting the valence band's atomic contributions. Using cubic symmetry, C11, C12, and C14 elastic constants were used to describe mechanical characteristics, and the Born criteria were met. Thus, mechanical stability was demonstrated for these compounds. Optical analyses exhibit changes concerning Ti concentrations and energy levels, including absorption spectra, conductivity, reflectivity, dielectric function, refractive index, energy loss function, and extinction coefficient. These findings shed light on the material's response to incident radiation and potential applications in hydrogen storage and optoelectronic devices.