Ab initio investigation of the electronic, optical, structural, mechanical, dynamical stability, and hydrogen storage properties of KXH3 (X = Hf and Zr) hydrides

Perovskite-type hydride materials offer potential for storing hydrogen, which is an essential way towards sustainable energy. In this study, the hydrogen storage, structural, mechanical, electronic, dynamic, and optical properties of KXH 3 (X = Hf, Zr) compounds were conducted using the CASTEP package. Phonon dispersion curves and negative formation enthalpies established the dynamic and thermodynamic stability of all of the compounds. In addition, their mechanical stability was affirmed through elastic constants meeting the Born criteria. Property assessments based on Pugh's B/G ratio, Cauchy pressure, and the anisotropic factor indicated their brittle nature, anisotropic behavior, and ionic bonding in these materials. The hydrogen storage capacities were found to be 1.37 wt% for KHfH 3 and 2.26 wt% for KZrH 3 , corresponding to the hydrogen desorption temperatures of 381.958 K and 468.765 K, respectively. Thus, the results highlight the prospects of KXH 3 hydrides in hydrogen storage technology.