Robust and eco-friendly double perovskites X₂AgFeBr₆ (X = Na, Li) simulations and exploration in terms of thermoelectric aspects

In this computational work, we simulated the robust and eco-friendly double perovskites X₂AgFeBr₆ (X = Na, Li) for the first time in detail for green energy harvesting applications involving thermoelectric generators. The structural, mechanical, and thermodynamic stability is assured from the Goldschmidt's tolerance and octahedral parameters, Burn-Haun criterion, formation energies, and phonon spectra respectively. The electronic band structures and density of states informed us the semiconducting nature of the compounds with band gaps of 4.81 eV, and 3.82 eV. The thermoelectric parameters like electrical conductivity close to ∼ 10¹⁷(Ωms)^-1, Seebeck coefficients up to 531.56 (μV/K), power factor in range of ∼ 10¹⁰ W/msk², and figure of merits close to one are observed at room temperature (T = 300 K). These fascinating results provide a theoretical basis for the synthesis of lead-free double perovskites X₂AgFeBr₆ (X = Na, Li), which find applications in thermoelectric devices.