Computational investigation of MgXH4 (X = Ti, Zr) complex hydrides: Predicting scalable and affordable hydrogen functional materials through DFT-based physical characterization

The development of lightweight, thermodynamically stable, and scalable hydrogen-functional materials is essential for enabling next-generation clean energy technologies. Transition-metal-incorporated magnesium-based hydrides have predicted as promising candidates for smart multifunctional materials due to their lightweight nature, high hydrogen density, and tunable physical properties. In this work, density functional theory (DFT) is employed to predict and characterize two previously unexplored tetragonal complex hydrides, MgXH 4 (X = Ti, Zr), with the aim of establishing their viability as affordable hydrogen-storage materials. Structural optimization combined with formation energy, reaction enthalpy, and zero-point energy (ZPE) corrections confirms excellent thermodynamic stability for both compounds, with ZPE values of 0.8901 eV (MgTiH 4 ) and 0.8725 eV (MgZrH 4 ). Phonon dispersion spectra without imaginary modes further establish their dynamical robustness. MgTiH 4 demonstrates superior gravimetric (5.29 wt%) and volumetric (141.89 kg/m 3 ) hydrogen capacities compared with MgZrH 4 (3.37 wt%, 123.81 kg/m 3 ), whereas MgZrH 4 exhibits a higher desorption temperature (761 K) relative to MgTiH 4 (599 K). Both hydrides exhibit high melting points (∼1200 K), moderate ductility (Poisson’s ratio 0.223–0.229), and metallic electronic behavior, while MgTiH 4 provides better heat transport through its higher lattice thermal conductivity (23.72 Wm −1 K −1 ) compared with MgZrH 4 (19.42 Wm −1 K −1 ). Mechanical stability and hardness values above 11 GPa support their resilience under operational conditions. Collectively, these results identify MgTiH 4 and MgZrH 4 as thermodynamically robust, mechanically durable, and technologically promising hydrogen-functional materials, offering valuable guidance for future experimental synthesis and scalable hydrogen storage applications.