Study of structural, elastic, electronic, optical, magnetic and thermoelectric characteristics of Hexafluoromanganets A₂MnF₆ (A = Cs, Rb, K) cubic double perovskites

We analyse a detailed investigation of structure, electronic, optical, magnetic and thermoelectric properties of (Cs, Rb, K)₂MnF₆ double perovskites with cubic Fm3¯m space group. The calculation method was the augmented plane-wave functions plus local orbitals as implemented in the WIEN2k code and the GGA followed by the most accurate GGA-mBJ as exchange potentials. The precision of our K₂MnF₆, Rb₂MnF₆ and Cs₂MnF₆ lattice constant compared with their available experimental data is in the range 1.2 % to 3.6 %. The calculated band gap of K₂MnF₆, Rb₂MnF₆ and Cs₂MnF₆ materials advantages them for use in light-emitting diode technology. These materials exhibit ferromagnetic behavior. The negative formation energy, free Helmholtz energy and the dispersion of phonons confirm their thermal, thermodynamic and dynamic stability. The calculated band gap of K₂MnF₆, Rb₂MnF₆ and Cs₂MnF₆ materials advantages them for use in light-emitting diode technology. The p-type charge carriers, direct band gap, and flat conduction and valence bands make them as good thermoelectric materials. The major contribution to the magnetization comes from the unfilled Mn-3d orbital. The high static dielectric constant reduces the recombination rate of charge carriers and the presence of absorption peaks in the ultraviolet region are advantageous in the exploitation in the optoelectronic field. The flat valence and conduction bands, high p-type conductivity, good thermoelectric parameters, as well as non-toxicity make these compounds mainly attractive in the thermoelectric application.