Structural, Electronic, Magnetic, and Thermoelectric Properties of Cr-doped DPs Cs2GeX6 (X= Cl, Br): DFT calculations
DOI:
https://doi.org/10.71330/thenucleus.2026.1520Abstract
Physical properties of chromium-doped halide double perovskites (DPs) Cs2GeX6 (X= Cl, Br) are estimated with respect to the DFT-based software Wein2k. These materials can be selected for solar cells and photovoltaics owing to their non-toxicity and ecological sustainability. Density functional theory (DFT) calculations investigate the physical characteristics of halides A2BX6 (A=Cs; B=Ge; X=Cl, Br), both pure and Cr-doped, which can potentially be applied to thermoelectric applications. Formation conditions and tolerance factors ensure the material's structural and thermodynamic feasibility. The band gap of the material Cs2GeCl6 is 4.5 eV; the same for the doped one Cs2Ge0.75Cr0.25Cl6 is 4.1 eV; the band gap of the material Cs2GeBr6 is 3.0 eV, while that of the doped material Cs2Ge0.75Cr0.25Br6 is 2.5 eV. Cs2Ge0.75Cr0.25Cl6 and Cs2Ge0.75Cr0.25Br6 have indirect band gaps, respectively. Furthermore, when the chromium doping ratio increases, so do the equilibrium lattice parameters of Cs2GeCl6 and Cs2GeBr6. Cs2GeCl6: 10.32 Å, Cs2Ge0.75Cr0.25Cl6: 10.55 Å, and Cs2GeBr6: 10.65 Å, Cs2Ge0.75Cr0.25Br6: 10.85 Å are the calculated lattice parameters. Both compounds have the same total magnetic moment values with 25% Cr doping for Cs2Ge0.75Cr0.25Cl6 and Cs2Ge0.75Cr0.25Br6. As a result, all of the halides investigated are commonly employed in thermoelectric devices. Thermal conductivity, electrical conductivity, and the Seebeck coefficient are also used to investigate thermoelectric properties. The computed values for PF at 200 K are PF=1.90 and 1.85 , and PF=3.98 and 4.09 at 800 K are measured for Cs2Ge0.75Cr0.25Cl6 and Cs2Ge0.75Cr0.25Br6, respectively, highlighting their importance in thermoelectric applications. The Seebeck coefficient value drops as temperature increases.
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