Exploring A2TiH6 (A = Li, Na) double perovskite hydrides as dual-functional materials for hydrogen storage and optoelectronics

초록

This work presents a comprehensive first-principles study on the structural stability, hydrogen storage capacity, elastic behavior, and optoelectronic properties of A2TiH6 (A = Li, Na) double perovskite hydrides. The cubic phase stability of both compounds is confirmed through formation energy analysis. The calculated gravimetric hydrogen storage capacities are 8.92 wt% for Li2TiH6 and 6.05 wt% for Na2TiH6, suggesting their suitability for efficient hydrogen storage. Elastic property analysis reveals strong mechanical anisotropy, with Li2TiH6 exhibiting ductile characteristics, whereas Na2TiH6 shows a brittle nature. The anisotropic behavior is further examined using various anisotropy indices and three-dimensional elastic moduli surfaces. Electronic band structure calculations confirm the semi-metallic character of both compounds. To explore their potential in energy-related applications, optical properties such as absorption coefficient, energy loss, refractive index, and dielectric function are analyzed. Both hydrides display strong optical responses in the ultraviolet region, indicating potential applications in optoelectronic and protective coating devices. Overall, this study identifies A2TiH6 (A = Li, Na) hydrides as promising candidates for future energy harvesting and hydrogen storage technologies.

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