The significance of anti‐fluorite Cs ₂ NbI ₆ via its structural, electronic, magnetic, optical and thermoelectric properties

Abstract

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.

Ab‐initio study of opto‐electronic and thermoelectric properties of direct bandgap double perovskites Rb 2 XGaBr 6 (XNa, K)

“…This code is obtained from CBT theory which is further used to calculate transport coefficient σ αβ (ε) of electrical conductivity. 42,43 The mathematical expression is given below: In the above equations, N, υβ (i, k), K and τ are the number of k-points, group velocity, wave vector and relaxation time, respectively. Integration of the transport coefficient gives other factors upon which thermoelectric response depends Here α, Ω, ƒ 0 , μ and β are tensor vector, unit cell volume, Fermi Dirac distribution, carrier concentration and charge on electron, respectively.…”

Optoelectronic and transport properties of Rb/ Cs 2 TeI 6 defective perovskites for green energy applications

“…A number of researchers carried investigations on materials in A 2 BX 6 group and reported them as excellent absorber to be used in solar cell applications. [4][5][6][7][8][9][10][11][12] Also materials of this group have been reported with excellent thermoelectric properties. [4][5][6][7] Among A 2 BX 6 defective perovskites, Rb/Cs 2 TeI 6 compounds have not been studies at experimental or theoretical level for solar cells and thermoelectric applications.…”

“…[4][5][6][7][8][9][10][11][12] Also materials of this group have been reported with excellent thermoelectric properties. [4][5][6][7] Among A 2 BX 6 defective perovskites, Rb/Cs 2 TeI 6 compounds have not been studies at experimental or theoretical level for solar cells and thermoelectric applications. Abriel 13 prepared Rb 2 TeI 6 and reported it with cubic A 2 BX 6 at 340 K. Sidey et al 14 reported lattice constant of Cs 2 TeI 6 as 11.700 Å from his experiment.…”

“…These materials are represented by A 2 BX 6 and termed as defective perovskites. A number of researchers carried investigations on materials in A 2 BX 6 group and reported them as excellent absorber to be used in solar cell applications 4‐12 . Also materials of this group have been reported with excellent thermoelectric properties 4‐7 .…”

Structural, electronic, optical and thermoelectric analysis of Rb/Cs2TeBr6 Vacancy ordered double perovskites

“…Vacancy ordered double perovskites, were widely studied as alternative of lead perovskites. As result, compounds of this class were proven as good conductors and have been considered as solar cell absorbers [14][15][16][17][18][19].This group of compounds is generally represented by A2BX6, where, A, B are cations, and X is a halide [20]. The structure of A2BX6 compounds has close similarity to the structure of cubic perovskite ABX3 with half of the B sites cation removed in an organized method.…”