The significance of anti‐fluorite <scp> Cs <sub>2</sub> NbI <sub>6</sub> </scp> via its structural, electronic, magnetic, optical and thermoelectric properties
Rehan Ullah, Malak Azmat Ali, G. Murtaza, Asif Mahmood, Shahid M. Ramay
Abstract
The structural, electronic, magnetic, optical and thermoelectric properties of anti-fluorite Cs2NbI6 were investigated using full potential augmented plane wave method of density functional theory. Structurally, Cs2NbI6 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 (Eg(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 Cs2NbI6 was explained on basis of crystal field theory. The calculated magnetic moment (1.001 μB) was found in reasonable agreement with experimental value. The optimum absorption and optical conductivity spectra in semiconductor state explored Cs2NbI6 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 Cs2NbI6 as potential optoelectronic and thermoelectric material, but can also inspire more experimental research on this important compound.