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    DFT assessment on the future prospects of inorganic lead-free halide double perovskites Cs2ABI6 (AB: GeZn, SnBe) for energy conversion technologies
    (Elsevier B.V., 2024) Caid, Messaoud; Rached, Habib; Rached, Djamel; Özışık, Hacı; Delig?z, Engin; Rached, Youcef
    In this study, we employed density functional theory (DFT) calculations to investigate the structural, elastic, electronic, optical, and thermoelectric properties of Cs2ABI6 (AB: GeZn, SnBe) halide double perovskites (HDPs). We employed the full-potential linear augmented plane-wave (FP-LAPW) method, incorporating the generalized gradient approximation (GGA) and Tran-Blaha modified Becke-Johnson (TB-mBJ) approach for the exchange-correlation potential. We found that the HDPs are stable in a cubic structure (space group Fm-3m), as indicated by phase stability analysis, formation energies, tolerance factor, and elastic constants. The compounds exhibits ductile behavior, as assessed by Poisson's and Pugh's ratios. The electronic band structures of Cs2GeZnI6 and Cs2SnBeI6 exhibit indirect band gaps (X-L) of 1.124 eV and 1.551 eV, respectively, as calculated using the TB-mBJ approximation. Optical spectra were evaluated over the 0–13 eV energy range, including the dielectric functions, extinction coefficient, electron energy loss, refractive index, optical conductivity, reflectivity, and absorption coefficient. Additionally, we calculated thermoelectric parameters across a range of chemical potentials and temperatures to assess their suitability for thermoelectric applications. Our results suggest that these compounds are highly promising candidates for both optoelectronic and thermoelectric devices.
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    Lead-Free Cs2(Cd/Sn)BeCl6 Halide Double Perovskites: a comprehensive first-principles study of structural, optoelectronic, and thermoelectric properties for sustainable energy applications
    (John Wiley and Sons Inc, 2025) Benkatlane, Aissa; Rached, Djamel; Caid, Messaoud; Rached, Habib; Deligöz, Engin; Rached, Youcef; Özışık, Hacı; Mansour, Houda; Benkhettou, Nour-Eddine
    Ab initio simulations based on density functional theory are employed to investigate the structural, electronic, mechanical, optical, and thermoelectric properties of Cs2ABeCl6 (A = Cd, Sn) halide double perovskites. The results demonstrate that both compounds crystallize in the stable cubic Fm-3m symmetry. Structural and thermodynamic stability are verified through the Goldschmidt tolerance factor (tG), octahedral factor (μ), modified tolerance factor (τ), formation energies (ΔEf), and Born–Huang criteria. Mechanical property evaluations suggest ductility and significant anisotropy in both compounds. First-principles calculations using the generalized gradient approximation indicate a direct bandgap of 1.98 eV for Cs2CdBeCl6 and an indirect bandgap of 2.58 eV for Cs2SnBeCl6. Optical investigations reveal significant absorption, refractive index, extinction coefficient, energy loss spectra, and reflectivity features in the energy range of 0–13 eV, indicating strong interactions within the ultraviolet region. Thermoelectric properties are evaluated using the BoltzTraP code, revealing low thermal conductivities and figure of merit values close to 1 at room temperature, which demonstrates excellent thermoelectric performance. The synergy of semiconducting behavior, strong UV absorption, and high thermoelectric efficiency positions Cs2CdBeCl6 and Cs2SnBeCl6 as promising candidates for optoelectronic and energy applications. This work presents the first theoretical investigation of beryllium-containing double perovskites, combining beryllium's unique mechanical stability with optoelectronic functionality.
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    Physical characteristics of Pb2FeSbO6 double perovskite for thermoelectric applications
    (Elsevier B.V., 2025) Caid, Messaoud; Rached, Djamel; Deligöz, Engin; Rached, Youcef; Rached, Habib; Irfani, Muhammad
    The structural, mechanical, electronic, magnetic, optical, and thermoelectric properties of Pb2FeSbO6 double perovskite are investigated using full-potential linear augmented plane-wave (FP-LAPW) method incorporating the generalized gradient approximation (GGA) and GGA plus onsite Coulomb parameter (GGA + U). Pb2FeSbO6 crystallizes in a ferromagnetic (FM) cubic structure (space group Fm-3m) with lattice constants of 8.072 Å, in good agreement with experimental data. The compound exhibits ductile behavior, as assessed by Poisson and Pugh's ratios. It shows an integer magnetic moment of 5.00μB per formula unit and demonstrates semiconductor behavior with bandgaps as follows: under GGA, the band-gap is 2.347eV (Γ-X) in spin-up and is 1.208eV (X-Γ) in spin-down; under GGA + U, the band-gap is 2.923eV (X-Γ) in spin-up and is 1.665eV (X-X) in spin-down. Optical properties reveal strong absorption in the ultraviolet range, and thermoelectric evaluation suggests a promising figure of merit (ZTmax ≈ 1.0 at 300 K). These findings underscore the potential of Pb2FeSbO6 for thermoelectric and optoelectronic applications
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    Unveiling the Potential of Ba2Zn5As6 and Ba2Zn5Sb6: A Comprehensive DFT Study
    (Wiley-VCH Verlag, 2025) Özışık, Hacı; Caid, Messaoud; Deligöz, Engin; Rached, Djamel; Rached, Youcef
    In this study, the structural, elastic, electronic, optical, and thermoelectric properties of Ba2Zn5X6 (X = As, Sb) compounds within the orthorhombic space group Pmna (No. 53) are investigated using density functional theory (DFT). The analysis of phonon dispersion and elastic constants confirms that the compounds are both dynamically and mechanically stable. These results indicate that the Ba2Zn5X6 (X = As, Sb) compounds have relatively low mechanical properties, indicating that they are likely to have low thermal conductivity. The vibrations of Ba atoms play an important role in the phonon thermal conductivity. In terms of electronic properties, the band structure analysis indicates that the compounds possess an indirect band gap (Gamma-Y). The calculation of optical properties in the energy range 0-12 eV reveals important information about dielectric functions, refractive index, reflection, optical conductivity, and absorption coefficient. These calculations have shown that the compounds exhibit good optical efficiency. Furthermore, a detailed investigation and discussion of their thermoelectric properties, such as Seebeck coefficient, electronic thermal conductivity, and power factor, indicate that these compounds can be candidates for thermoelectric devices. These calculations provide valuable insights into enhancing the thermoelectric performance of these compounds.