Comparative DFT Study of K2AgSbBr6 and K2NaScBr6: Exploring the Role of B′B″ Cation Substitution on Material Properties

The effects of cation substitution are the main emphasis of this investigation into the structural, mechanical, electronic, and optical properties of double perovskites K2AgSbBr6 and K2NaScBr6. Outwardly favorable tolerance and octahedral factors and negative formation energy confirmed structural stability and thermodynamic feasibility. Mechanical analysis showed that K2AgSbBr6 possesses greater volumetric stability and rigidity, while K2NaScBr6 exhibits greater ductility and isotropic characteristics. The electronic properties determined based on density functional theory (DFT) calculations indicate that K2AgSbBr6 has an indirect bandgap of 0.857 eV, making it suitable for applications using visible light, and K2NaScBr6 has a direct bandgap of 3.107 eV, making it ideal for UV-specific technologies. Optical analyses demonstrate complementary characteristics, particularly in terms of the dielectric function, absorption, reflectivity, energy loss function, refractive index, extinction coefficient, and optical conductivity. K2AgSbBr6 exhibits strong visible light absorptivity.