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<p>In this work, a comprehensive first-principles investigation of the structural, elastic, electronic, magnetic, optical, thermoelectric, and thermodynamic properties of lead-free double perovskites Rb₂AgMnX<sub>6</sub> (X = Cl, Br, I) is presented using the FP-LAPW method within density functional theory. The optimized lattice constants are found to be 10.77&#xa0;Å, 11.52&#xa0;Å, and 11.85&#xa0;Å for Rb₂AgMnCl<sub>6</sub>, Rb₂AgMnBr<sub>6</sub>, and Rb₂AgMnI<sub>6</sub>, respectively, confirming lattice expansion with increasing halogen size, while formation energies of − 1.4&#xa0;eV, − 1.03&#xa0;eV, and − 1.97&#xa0;eV indicate thermodynamic stability, with the iodide compound being the most stable. Elastic analysis reveals mechanical stability for all compounds, with bulk moduli of 9.92 GPa, 4.68 GPa, and 9.15 GPa, and Pugh ratios of 2.05, 3.24, and 2.34, confirming ductile behavior. Electronic band structure calculations show half metallic nature with band gaps of 3.76, 3.10, and 1.89&#xa0;eV (GGA), reduced to 2.43, 1.81, and 1.15&#xa0;eV (GGA + U), and further refined to 2.30, 1.63, and 0.95&#xa0;eV using HSE06 for Cl<sup>−</sup>, Br<sup>−</sup>, and I<sup>−</sup> based compounds, respectively. Density of states analysis reveals strong Mn–d contributions near the conduction band and significant Ag–d/X–p hybridization in the valence band. Magnetic calculations yield a constant total magnetic moment of 4.00 µ<sup>Tot</sup>(µ<sub>B</sub>) for all compounds, dominated by Mn (4 µ<sup>Tot</sup>(µ<sub>B</sub>), indicating robust ferromagnetic ordering. Thermoelectric analysis shows that Rb₂AgMnI₆ exhibits superior performance with a maximum ZT of 0.85, compared to 0.25 and 0.20 for Cl and Br compounds, respectively, due to reduced thermal conductivity (0.6 W/mK) and enhanced power factor (3.5 × 10<sup>11</sup> W/mK<sup>2</sup>s). Optical properties demonstrate strong absorption in the visible region with functional-dependent spectral variations. Overall, the tunable electronic structure, stable ferromagnetism, and promising thermoelectric efficiency suggest that Rb₂AgMnX<sub>6</sub> compounds are excellent candidates for optoelectronic, spintronic, and energy harvesting applications.</p>

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Spin-polarized energy conversion in lead-free Rb₂AgMnX₆ double perovskites: a first-principles perspective

  • 期刊论文

  • 发表日期：

    2026年7月20日

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  • Mubashir Hussain,
  • Amir Ullah,
  • Eman M. Alshehri,
  • Fatimah M. Alzahrani,
  • M. Naziruddin Khan,
  • Hind Albalawi,
  • Mohammad Sohail,
  • Tahir Zaman,
  • Hamza Rekab-Djabri,
  • Nasir Rahman

摘要

In this work, a comprehensive first-principles investigation of the structural, elastic, electronic, magnetic, optical, thermoelectric, and thermodynamic properties of lead-free double perovskites Rb₂AgMnX6 (X = Cl, Br, I) is presented using the FP-LAPW method within density functional theory. The optimized lattice constants are found to be 10.77 Å, 11.52 Å, and 11.85 Å for Rb₂AgMnCl6, Rb₂AgMnBr6, and Rb₂AgMnI6, respectively, confirming lattice expansion with increasing halogen size, while formation energies of − 1.4 eV, − 1.03 eV, and − 1.97 eV indicate thermodynamic stability, with the iodide compound being the most stable. Elastic analysis reveals mechanical stability for all compounds, with bulk moduli of 9.92 GPa, 4.68 GPa, and 9.15 GPa, and Pugh ratios of 2.05, 3.24, and 2.34, confirming ductile behavior. Electronic band structure calculations show half metallic nature with band gaps of 3.76, 3.10, and 1.89 eV (GGA), reduced to 2.43, 1.81, and 1.15 eV (GGA + U), and further refined to 2.30, 1.63, and 0.95 eV using HSE06 for Cl−, Br−, and I− based compounds, respectively. Density of states analysis reveals strong Mn–d contributions near the conduction band and significant Ag–d/X–p hybridization in the valence band. Magnetic calculations yield a constant total magnetic moment of 4.00 µTot(µB) for all compounds, dominated by Mn (4 µTot(µB), indicating robust ferromagnetic ordering. Thermoelectric analysis shows that Rb₂AgMnI₆ exhibits superior performance with a maximum ZT of 0.85, compared to 0.25 and 0.20 for Cl and Br compounds, respectively, due to reduced thermal conductivity (0.6 W/mK) and enhanced power factor (3.5 × 1011 W/mK2s). Optical properties demonstrate strong absorption in the visible region with functional-dependent spectral variations. Overall, the tunable electronic structure, stable ferromagnetism, and promising thermoelectric efficiency suggest that Rb₂AgMnX6 compounds are excellent candidates for optoelectronic, spintronic, and energy harvesting applications.