Investigation of the Structural, Mechanical, Electronic, Optical, Dynamic, and Thermodynamic Characteristics of XMgH 3 (X = K, Rb, Cs) for Potential Use in Hydrogen Storage Applications

ABSTRACT This research utilizes theoretical approaches to explore the structural and physical characteristics of XMgH 3 (X = K, Rb, Cs) materials. The lattice parameters of XMgH 3 (X = K, Rb, Cs) metal hydrides are determined to be 4.0493, 4.1293, and 4.2746 Å, respectively. The mechanical, thermodynamic, and dynamic stabilities of the XMgH 3 compounds are verified through the analysis of elastic constants, formation energy, and phonon dispersion. The calculated B / G ratios indicate that XMgH 3 compounds display brittle behavior. Additionally, our results show that XMgH 3 (X = K, Rb, Cs) possesses an indirect band gap of 2.13, 1.96, and 1.64 eV in its cubic crystalline phase. Additionally, the hydrogen storage capacities of KMgH 3 , RbMgH 3 , and CsMgH 3 are measured at 4.55, 2.68, and 1.89 wt%, respectively, with associated hydrogen desorption temperatures of 1631.4, 1594.5, and 1565.0 K. This work addresses the existing data deficiencies regarding XMgH 3 (X = K, Rb, Cs) and offers valuable insights into their fundamental physical properties.