A comprehensive DFT of structural, electrical, elastic, and optical properties of CsGeF3 perovskite under hydrostatic pressure

Abstract

In this paper, we applied first-principles theory to calculate the structural stability, electronic properties, elasticity, and optical behavior of the halide metal perovskite CsGeF₃ under pressures ranging from 0 to 40 GPa. The optimal lattice constants were determined using the Birch-Murnaghan method, yielding an equilibrium lattice constant (a₀) of 4.56 Å and a bulk modulus (B₀) of 49.35 GPa at 0 GPa. According to mechanical stability criteria and formation energies, the material possesses a stable crystal structure. Studies of electronic properties indicate that CsGeF₃ is a direct bandgap semiconductor. The bandgap decreases as pressure increases. Based on the Cauchy pressure, Pugh's ratio, and Poisson's ratio, the material is considered to exhibit high ductility at 0 GPa, with its ductility is further enhanced as pressure increases. The dielectric function, absorption coefficient, conductivity, and reflectivity were also investigated. Results indicate that as the pressure increases, the intensity of the absorption coefficient increases and exhibits a red shift. Furthermore, this material exhibits the ability to absorb light in the visible and lower ultraviolet region, indicating its potential as a UV detector.