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The structural, electronic, magnetic, optical and thermoelectric properties of anti-fluorite Cs 2 NbI 6 were investigated using full potential augmented plane wave method of density functional theory. Structurally, Cs 2 NbI 6 was found to be cubic in ground state from values of tolerance factor (1.04) and formation energy (−22.3 eV). While, it's ferromagnetic nature was predicted from volume optimization process. In spin down channel, the compound was explored as indirect band gap (E g(Γ-X) = 1.97 eV) semiconductor, while it changes to metallic in upper spin channel. Nb-d and I-p states were exposed as the main cause of spin dependent electronic nature (half-metallicity). The origin of magnetism in Cs 2 NbI 6 was explained on basis of crystal field theory. The calculated magnetic moment (1.001 μ B) was found in reasonable agreement with experimental value. The optimum absorption and optical conductivity spectra in semiconductor state explored Cs 2 NbI 6 as suitable for optoelectronic devices. Furthermore, the transport properties were calculated using BoltzTrap code. The nature of carriers was predicted as n type from negative values of Seebeck coefficients. Where, the figure of merit (ZT) was found to increase up to 0.85 at 900 K. The present work not only explores Cs 2 NbI 6 as potential optoelectronic and thermoelectric material, but can also inspire more experimental research on this important compound.

This first principles study explores the structural, electronic, optical, and thermoelectric properties of the CsTmCl3 halide perovskite using density functional theory. The structural and thermoelectric properties are calculated without considering the spin‐orbit coupling (SOC), while both the electronic and optical properties are calculated with and without the SOC effect. A comparison of the results obtained with and without SOC reveals that inclusion of the SOC effect reduces the band gap from 1.18 to 0.99 eV due to shifting of the Tm‐d states toward the Fermi level. However, direct nature of the band gap remains the same in both the cases. The effect of SOC on the optical properties is, however, only visible in shifting of the third characteristic peak to lower energies. Strong optical absorption in the visible and ultraviolet regions shows effectiveness of CsTmCl3 in the optical devices working in these regions. Moreover, the calculated transport properties reveal CsTmCl3 as a useful thermoelectric material at room temperature.

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