Physical Properties of Transition Metal Hydride Superconductors Mg ₂ Tm H ₆ ( Tm

ABSTRACT

In this work, a comprehensive first‐principles investigation of structural, hydrogen storage potential, electronic, elastic, mechanical, thermophysical, superconducting, and optical properties of Mg ₂ Tm H ₆ ( Tm = Rh, Pd, Ir, Pt) hydrides is presented. These compounds exhibit favorable mechanical and dynamical stability, while Mg ₂ Tm H ₆ ( Tm = Rh, Ir, Pt) are thermodynamically stable and Mg ₂ PdH ₆ is metastable. Their gravimetric hydrogen‐storage capacities range from 2.42 to 3.84 wt.%. All behave as ductile, elastically anisotropic, and exhibit weak metallic character, reflected in the elastic hierarchy C ₁₁ > C ₁₂ > C ₄₄ ​ as well as the moduli trend Y > B > G . Mg ₂ PtH ₆ possesses the largest bulk modulus. In contrast, Mg ₂ IrH ₆ exhibits the highest Young's modulus, superior machinability, and excellent dry lubricity. Electronic structures show low density of states at the Fermi level, with predicted superconducting transition temperatures of 25–44 K. Thermophysical calculations reveal their stability and efficient heat transport. Optical studies indicate high reflectivity in the infrared and visible regions, and strong UV absorption. Optical conductivity suggest potential for UV optoelectronic devices, photodetectors, and reflective coatings. These results demonstrate that Mg ₂ Tm H ₆ hydrides combine favorable hydrogen storage, mechanical robustness, superconductivity, and multifunctional optical properties, making them promising candidates for energy storage, superconducting, and advanced optoelectronic applications.