Ab initio Study of Ag-Based Fluoroperovskite AgMF₃ (M = Co and Ni) Compounds

Abstract

Ab initio calculations of Ag-based fluoroperovskite AgMF₃ (M = Co and Ni) compounds are investigated using the full-potential linearized augmented plane wave method. Wien2k and BoltzTrap codes are used to calculate the different physical properties. The structural parameters of the present compounds are within reasonable agreement with previous calculations. This study shows that AgCoF₃ and AgNiF₃ are anisotropic, ductile, mechanically and thermodynamically stable␣compounds, where AgCoF₃ is found to be stiffer and less compressible than AgNiF₃. The spin-polarized electronic band structure illustrates that AgCoF₃ is metallic, while AgNiF₃ is a semiconductor with indirect (M–Г) band gap energy of 0.43 eV. The bonding force between atoms is found to be mainly ionic with some covalent nature. The total magnetic moment of AgCoF₃ (3.04 μ _B) is found to be higher than that calculated for AgNiF₃ (2.00 μ _B). Using the magnetic susceptibility calculations, AgCoF₃ is classified as antiferromagnetic, whereas AgNiF₃ is a ferromagnetic compound. The calculated static refractive index of AgCoF₃ (3.85) and AgNiF₃ (3.60) is inversely proportional with the energy band gap. Suitable␣applications are predicted for AgCoF₃ and AgNiF₃ based on their absorption and reflection properties. Furthermore, beneficial thermoelectric applications are expected for the present compounds due to their large Seebeck coefficient ($S_{{{\rm{AgCoF}}_{ 3} }} = 2.92 \times 10^{3} \,\, \mu {\hbox{V/K}}\,\,{\hbox{and}}\,\,\,S_{{{\rm{AgNiF}}_{3} }} = 2.84 \times 10^{3} \,\,\mu {\hbox{V/K}}$) and their thermoelectric power factor with respect to relaxation time ($S^{2} \sigma /t_{{AgNiF_{3} }} = 1.11 \times 10^{9} \,\,{\hbox{W/K}}^{ 2} \,\,{\hbox{and}}\,\,S^{2} \sigma /t_{{AgNiF_{3} }} = 1.28 \times 10^{11} \,\,{\hbox{W/K}}^{ 2}$).