Akademik Veri Yönetim Sistemi
Materials Today Communications, cilt.54, 2026 (SCI-Expanded, Scopus)
Thallium hexafluorosilicate (Tl₂SiF₆) is a cubic inorganic fluoride compound crystallizing in the Fm -3 m space group with lattice parameter a = 8.39 Å. Despite the growing interest in halide-based wide-gap semiconductors for photovoltaic, optoelectronic, and thermoelectric device applications, the fundamental properties of Tl₂SiF₆ have remained largely unexplored. In this work, we present a systematic ab initio investigation of the structural, dynamic, electronic, optical, and thermoelectric characteristics of Tl₂SiF₆ using density functional theory (DFT) as implemented in the full-potential linearized augmented plane-wave (FP-LAPW) code WIEN2k. Structural optimization via the Birch–Murnaghan equation of state confirms thermodynamic stability at the equilibrium volume of 590.88 ų with a density of 6.19 g/cm³. Phonon dispersion and phonon density of states calculations confirm the dynamic stability of the cubic phase, with no imaginary frequency modes observed across the entire Brillouin zone. Electronic band structure calculations employing both the generalized gradient approximation (GGA) and the modified Becke–Johnson (mBJ-GGA) exchange-correlation potential reveal an indirect wide band gap of 5.0 eV (GGA) and 6.2 eV (mBJ-GGA), classifying Tl₂SiF₆ as a wide-gap insulator. Optical spectra, including the real and imaginary parts of the dielectric function, refractive index, absorption coefficient, extinction coefficient, and energy loss function, are analyzed and discussed in relation to the electronic structure. A static refractive index of 1.38 (mBJ) indicates excellent optical transparency in the visible range, making this compound a candidate for UV-transparent coating applications. Thermoelectric transport properties computed via the BoltzTraP code yield a Seebeck coefficient rising from 137 to 788 μV/K across 100–1000 K, indicating a large Seebeck response near the valence band edge. However, due to the wide band gap of Tl₂SiF₆, its intrinsic electrical conductivity is expected to be limited, and thermoelectric performance requires carrier-concentration optimization. Quasi-harmonic approximation (QHA) thermodynamic analysis reveals temperature-dependent trends in free energy, entropy, and heat capacity, with Cᵥ converging to the Dulong–Petit limit above 600 K. Collectively, these results establish Tl₂SiF₆ as a multifunctional material of significant interest for UV-optics and high-temperature applications, while its thermoelectric potential requires further transport optimization.