Decoding the hydrogen storage and functional properties of MgBH₃ (B = Mo and In) via first-principles simulations

This present study presents a complete first-principles investigation of the structural, hydrogen storage, optoelectronic, mechanical, and thermodynamic properties of MgBH₃ (B = Mo, In). Cubic phase structural stability was determined by formation energies, Goldschmidt tolerance factors, and octahedral factors. Hydrogen storage capacities were calculated as 2.45 wt% for MgMoH₃ and 2.13 wt% for MgInH₃, indicating reasonable desorption suitable for real-world energy storage. Electronic structure calculations (GGA-PBE) determine metallic conductivity as a result of valence and conduction band overlap. Optical analyses show that the high refractive index and strong absorption of MgBH₃, combined with their metallic nature, ensure efficient charge transport and lattice stability. Mechanical stability is confirmed by the elastic constants satisfying Born's criteria. This stability, coupled with their distinct ductile nature, ensures robust structural integrity and prevents microcracking, making repeated hydrogen cycling highly stable. Strong elastic anisotropy is indicative of the directional dependence of hydride perovskites. Thermodynamic assessment: Debye temperature, lattice and minimum thermal conductivities, and Grüneisen parameter offer insight into phonon transport and heat capacity, confirming their utility as thermal barrier coatings at high temperatures. In short, MgBH₃ (B = Mo, In) hydrides are multifunctional materials exhibiting moderate hydrogen-storage capability, robust mechanical stability, favorable thermal-management characteristics, and distinct dielectric and metallic optical responses.