Insight into the physical properties of Rb₂YCuX₆ (X = Br and I) lead-free elpasolite for high-energy applications

This study explores the intriguing properties of lead-free Rb2YCuX6 (X = Br and I) elpasolite, a novel class of A(2)B'B'X-6 double perovskite materials, focusing on their structural, mechanical, and optoelectronic characteristics. The stability of the cubic structures was rigorously confirmed by calculating the tolerance factor, and octahedral factor, and employing the Birch-Murnaghan equation of states. Mechanical stability was confirmed through the examination of various parameters, revealing the materials as incompressible, hard, ductile, and anisotropic double perovskites. Analyzing the electronic band structure and density of states unveiled a distinctive indirect band gap of 2.46 eV for Rb2YCuBr6 and 2.12 eV for Rb2YCuI6, from L-X symmetry points. The optical parameters of these double perovskites were computed to evaluate their use in optical devices. Notably, their minimal light scattering, refractive index ranging from approximately 1.5 to 2, and broad absorption band within the visible spectrum make them highly suitable for optoelectronic applications, emphasizing their potential role in energy conservation and high-energy scenarios.