Computational study of the mechanical stability, hydrogen storage and optoelectronic properties of new perovskite hydrides CsXH3 (X = Ca, Sr and Ba)

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In this study, the physical properties of the perovskite hydrides CsXH3 (X = Ca, Sr and Ba) were explored using density functional theory (DFT) to assess their suitability for optoelectronic and hydrogen storage applications. The properties analyzed for these materials included hydrogen storage capacity, as well as structural, mechanical, electronic, and optical characteristics. These investigations were conducted using the GGA-PBE method within the ABINIT simulation code. Initially, the structural properties revealed that the lattice constants of the optimized unit cell structures of CsCaH3, CsSrH3 and CsBaH3 are 4.66, 4.80 and 5.25 Å, respectively. Additionally, the formation energy calculations proved that the selected materials are thermodynamically stable and can be synthesized. The mechanical stability of such hydrides has been confirmed by the results of the elastic constants that met the necessary stability criteria. Moreover, the hydrogen storage properties of the considered compounds revealed capacities of 1.71 wt%, 1.35 wt%, and 1.11 wt% for CsCaH3, CsSrH3 and CsBaH3, respectively, indicating their considerable potential as candidates for hydrogen storage applications. The electronic properties revealed that the three investigated materials exhibit semiconducting behavior with band gaps of 3.16, 2.84 and 2.18 eV for CsCaH3, CsSrH3 and CsBaH3, respectively. Additionally, various optical features including real ε1(ω) and imaginary ε2(ω) dielectric components, refractive index n(ω), absorption factor α(ω) were also investigated and implied that CsCaH3, CsSrH3 and CsBaH3 are suitable for optoelectronic devices. This study is the first to highlight the relevance of new materials CsCaH3, CsSrH3 and CsBaH3 for hydrogen storage and optoelectronic applications.