First-principles quantum insight of alkali-titanium hydrides XTi3H9 (X = Li, Na, K) for hydrogen storage and optoelectronics applications

초록

This study utilized first-principles density functional theory (DFT) to thoroughly examine the structural, mechanical, electrical, optical, and hydrogen storage characteristics of titanium-based perovskite-type hydrides XTi3H9 (X = Li, Na, K). The optimized lattice constants of 4.481 & Aring;, 4.544 & Aring;, and 4.764 & Aring; for LiTi3H9, NaTi3H9, and KTi3H9, respectively, show that the cubic phases are stable, as shown by XRD simulations. The negative formation energies show that the system is thermodynamically stable, and the estimated elastic constants meet the Born stability criterion, which shows that the system is mechanically strong. Studies of electronic band structure and density of states demonstrate that metals conduct electricity, which makes it easier for hydrogen to stick to and move through them. Optical tests show that the material has a strong dielectric response and high refractive index, which means it could be useful in optoelectronic devices. The calculated gravimetric hydrogen storage capacities are 5.68 wt% for LiTi3H9, 5.16 wt% for NaTi3H9, and 4.73 wt% for KTi3H9, which is close to or to the U.S. DOE's 2025 goal for solid-state hydrogen storage. These results offer novel perspectives on Ti-based perovskite hydrides as versatile materials for sustainable hydrogen energy and optoelectronic applications.

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