First principles investigation for the hydrogen storage properties of novel lithium-based XLiH3 (X=K, Rb) perovskite-type hydrides for advance hydrogen storage system.

In this work, the density functional theory is used to investigate the structural, mechanical, electronic, dynamic, thermodynamic, optical and hydrogen storage properties of XLiH 3 (X = K, Rb) for the first time. Both KLiH 3 and RbLiH 3 materials exhibit dynamic, mechanical and thermodynamic stability. The lattice parameters of KLiH 3 and RbLiH 3 are 3.908 and 4.070 Å, respectively. The investigation of Cauchy pressure, Poisson's ratio and B/G ratio shows that KLiH 3 and RbLiH 3 are brittle materials. Moreover, the electronic properties of XLiH 3 hydrides demonstrate that KLiH 3 and RbLiH 3 show metallic nature. Optical properties of these compounds are studied and reveal that they have very high refractive indexes and dielectric functions. The thermodynamic properties, including heat capacity, entropy, enthalpy, and free energy of XLiH 3 , are investigated as well. The hydrogen storage capacities of KLiH 3 and RbLiH 3 are 5.805 and 3.071 wt%, respectively, confirming that KLiH 3 has a high hydrogen storage capacity and is more suitable as a hydrogen storage material. Our study opens up a new-pathway for designing novel hydrogen storage materials. • XLiH 3 (X = K, Rb) perovskite hydrides have been investigated using first-principles. • XLiH 3 (X = K, Rb) exhibit thermodynamic, mechanical, and dynamical stability. • The hydrogen storage capacity of XLiH 3 is 5.805 wt% and 3.071 wt%, respectively. • Our studies propose that KLiH 3 is a more suitable hydrogen storage material. [ABSTRACT FROM AUTHOR]