Computational analysis of the X₂H₃I (X=Ca or Sr) compounds for hydrogen storage: A DFT approach

This study presents an in-depth investigation into the physical properties of X₂H₃I (X = Ca or Sr) compounds, using density functional theory (DFT) as implemented in the Wien2k package. The analysis spans a range of properties, including structural, electronic, optical, and thermoelectric characteristics. The electronic structure calculations reveal that both compounds are non-magnetic semiconductors, with band gaps of 2.815 eV for Ca₂H₃I and 3.613 eV for Sr₂H₃I. The optical properties were also explored, with a focus on the absorption coefficient, where a notable peak was identified predominantly in the infrared region. For Sr₂H₃I, the highest absorption intensity was observed in the zz direction, whereas for Ca₂H₃I, significant absorption was noted in the xx and yy directions. Additionally, the Seebeck coefficient was studied as a function of temperature, showing an increasing trend, indicating that these materials have a higher potential to generate electrical voltage under a temperature gradient, making them promising candidates for thermoelectric applications. Moreover, the hydrogen storage potential was evaluated, with gravimetric capacities of approximately 1.419 wt% for Ca₂H₃I and 0.981 wt% for Sr₂H₃I.