First-principles Quantum analysis of novel X4Mg3H14 (X= Li and Na) hydrides: Structural, optoelectronic, and hydrogen storage frontiers

Solid-state hydrogen storage is essential for the progression of sustainable energy technologies, and perovskite hydrides have surfaced as viable options. In this study, we utilize density functional theory (DFT) to examine the structural, electrical, optical, and hydrogen storage characteristics of new X₄Mg₃H₁₄ (X = Li and Na) hydrides. The structural study verifies their thermodynamic and dynamic stability, with Li₄Mg₃H₁₄ demonstrating superior stability compared to Na₄Mg₃H₁₄. Electronic band structures and density of states show that both compounds act like metals. Optical studies reveal notable dielectric responses, absorption peaks, and reflectivity, indicating possible optoelectronic uses. The gravimetric hydrogen storage capabilities are 12.29 wt% for Li₄Mg₃H₁₄ and 7.88 wt% for Na₄Mg₃H₁₄. These numbers meet and exceed the U.S. DOE goal. The predicted desorption temperatures (335 K for Li₄Mg₃H₁₄ and 339 K for Na₄Mg₃H₁₄) show that these materials can be stored at high temperatures. These results show that X₄Mg₃H₁₄ hydrides, especially Li₄Mg₃H₁₄, are good candidates for solid-state hydrogen storage applications.