First principle study of structural, electronic, optical and mechanical properties of cubic fluoro-perovskites: (CdXF₃, X = Y, Bi)

Abstract

The full-potential linearized augmented plane wave (FP-LAPW) process is applied for the investigation of structural, mechanical, electronic and including optical properties of cubic perovskites CdXF₃ (X = Y, Bi). For the consideration of the exchange–correlation potential, the generalized gradient approximation and the modified Becke–Johnson are implemented. The structural properties, comprising equilibrium lattice constant, the bulk modulus and its pressure derivative are calculated and found that both the compounds are structurally stable in its cubic crystal. Elastic properties including anisotropy factor, elastic constants, Poisson's ratio, shear modulus and Young's modulus are calculated. In elastic properties the higher bulk modulus and B/G ratio yields that these compounds are very hard and ductile in nature. Furthermore, these materials show resistance to plastic deformation ascribed to high value of shear modulus “G.” Calculations of electronic band structure, density of states and electronic charge density indicate that CdYF₃ compound has an indirect energy band gap of 2.056 eV from (M-X) while CdBiF₃ represents a direct band gap of about 1.027 eV from (M-M). The mixture of ionic and covalent bonding character is found in both CdXF₃ (X = Y, Bi) compounds. To investigate and evaluate the contribution of states to the various bands, the full and partial density of states are exploited. Calculations of the optical spectrum like real ε₁(ω) and imaginary ε₂(ω) components of dielectric function, optical reflectivity [R(ω)], absorption coefficient [I(ω)], optical conductivity [σ(ω)], refractive index [n(ω)], extinction coefficient and electron energy loss are carried out for the energy range of 0–40 eV. Various transitions between bands were calculated from the imaginary part of the dielectric function. From above examinations, it is deemed that these mixes may include thorough understanding in structuring the prime electronic gadgets. All of the properties are reported for the first time for CdXF₃ (X =  Y, Bi).