Pressure-driven semiconducting to metallic transition in francium tin trihalides (FrSnX3) perovskite

What is it about?

This study investigates the properties of halide-based perovskite FrSnX3 (X = Cl, Br, and I) under hydrostatic pressures from 0 to 6 GPa using first-principles calculations based on density functional theory. The compounds are found to be stable and ductile, with decreasing bandgaps under pressure, transforming from semiconductors to conductors. Optical properties improve under pressure, with high absorption in the 10-13 eV range, making them suitable for UV applications. Reflectivity and refractive index also increase with pressure. Elastic properties indicate increased hardness and ductility, while magnetic properties remain unchanged as diamagnetic. These findings suggest that FrSnX3 compounds are promising for photovoltaic cells, UV light absorbers, and optoelectronic devices.

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Photo by Mariana Proença on Unsplash

Photo by Mariana Proença on Unsplash

Why is it important?

This study highlights several key findings regarding the halide-based perovskite FrSnX3 (X = Cl, Br, and I) under varying hydrostatic pressures (0 to 6 GPa): Stability and Ductility: The compounds FrSnCl3, FrSnBr3, and FrSnI3 are mechanically stable and ductile, as determined by formation enthalpy and elastic constant calculations. Semiconductor Properties: At ambient pressure, these materials are semiconductors with bandgaps of 1.046 eV, 0.675 eV, and 0.485 eV for FrSnCl3, FrSnBr3, and FrSnI3, respectively. Bandgap Variation with Pressure: Under increasing pressure, the bandgaps decrease, reaching 0 eV at 6 GPa, 4 GPa, and 2 GPa for FrSnCl3, FrSnBr3, and FrSnI3, respectively, indicating a transition from semiconductor to conductor. Optical Properties: High pressure enhances the optical absorption in the 10–13 eV range, with chlorine showing the highest and iodine the lowest absorption. Reflectivity and refractive index also increase with pressure, with chlorine having a lower refractive index compared to iodine. Dielectric Properties: The dielectric constant ranges from 4.5 to 7.5 F/m and increases with pressure, indicating improved charge storage capacities, especially for iodine. Mechanical Enhancement: Hydrostatic pressure enhances the hardness and ductility of these compounds, as evidenced by increased bulk, Young’s, and shear modulus, and elastic constants. Magnetic Properties: The diamagnetic nature of these compounds remains unaffected by pressure. Potential Applications: The material's exceptional absorption properties and transition from semiconductor to conductor under pressure make it suitable for photovoltaic cells, ultraviolet light absorbers, and optoelectronic devices. In summary, this research provides valuable insights into the pressure-dependent mechanical, optical, and electronic properties of FrSnX3 perovskites, highlighting their potential for advanced technological applications.

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