DENSITY FUNCTIONAL THEORY ANALYSIS OF LI-DOPED RbMgF3 FOR X-RAY DOSIMETRY AND SENSOR APPLICATIONS

Abstract

Perovskite materials have attracted considerable attention in recent years due to their remarkable structural flexibility and wide range of applications in optoelectronic and photonic devices. Among these materials, fluoride-based perovskites exhibit excellent chemical stability, wide band gaps, and strong optical responses, making them promising candidates for advanced technological applications. In the present study, a comprehensive theoretical investigation of Li-doped RbMgF₃ perovskite is carried out using first-principles calculations based on density functional theory (DFT). The aim of this work is to explore the influence of lithium doping on the structural stability, electronic characteristics, mechanical behavior, optical properties, and X-ray diffraction patterns of the RbMgF₃ crystal. The structural properties of Li-doped RbMgF₃ are first analyzed through geometry optimization using the generalized gradient approximation (GGA) within the plane-wave pseudopotential framework. The optimized lattice parameters confirm that the compound maintains a stable cubic perovskite structure after lithium incorporation. The calculated total energy minimization demonstrates the thermodynamic stability of the doped system. To further evaluate the mechanical stability of the material, the elastic constants are computed. The obtained elastic parameters satisfy the Born mechanical stability criteria for cubic crystals, confirming that Li-doped RbMgF₃ is mechanically stable. Additional mechanical parameters such as bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio are derived from the elastic constants, providing deeper insight into the mechanical strength and ductility of the compound.The electronic properties of Li-doped RbMgF₃ are investigated through band structure calculations and density of states (DOS) analysis. The calculated electronic band structure reveals that the compound exhibits semiconducting behavior with a wide band gap. The total and partial density of states indicate that the valence band is mainly dominated by fluorine states, while the conduction band is primarily contributed by magnesium and rubidium orbitals. The incorporation of lithium introduces slight modifications in the electronic states, which may influence the electrical and optical performance of the material. These electronic characteristics suggest that Li-doped RbMgF₃ can be considered a suitable candidate for optoelectronic and ultraviolet optical devices. Furthermore, the optical properties of the compound are examined by calculating the complex dielectric function and related optical parameters, including refractive index, absorption coefficient, reflectivity, and optical conductivity. The results indicate strong optical absorption in the ultraviolet region and low absorption in the visible range, which is desirable for UV optoelectronic applications. The refractive index and reflectivity spectra also show stable optical behavior across a wide energy range, highlighting the potential of this material for photonic and optical device applications. Finally, simulated X-ray diffraction (XRD) patterns are generated to verify the crystalline structure and phase stability of Li-doped RbMgF₃. The XRD peaks correspond well with the characteristic reflections of the cubic perovskite structure, confirming the preservation of the crystal symmetry after lithium doping. Overall, the present theoretical investigation demonstrates that Li-doped RbMgF₃ possesses favorable structural stability, mechanical robustness, and promising electronic and optical properties. These findings suggest that this material could be a potential candidate for future applications in optoelectronic, photonic, and ultraviolet device technologies.