Investigation of thermoelectric properties of 2D β-silicon monotelluride (site)

Abstract

Thermoelectric properties of novel 2D silicon monotelluride (SiTe) are studied using first principles calculations. The plane wave method based on density functional theory as implemented in Vienna ab initio simulation package (VASP) is used to calculate the electronic structure. For the exchange correlation functionals, the generalized gradient approximation developed by Perdew-BurkeErnzerhof (PBE-GGA) is taken into account. The calculated band gap for β-SiTe is 1.83 eV which is in consistence with the previous theoretical data. The electronic and lattice transport properties are investigated using the Boltzmann transport equation. For the electronic transport properties, BoltzTraP code is used which relies on the Fourier interpolation of electronic band structure and thus requires a large k-sampling to optimize the interpolation and produce better results. The Seebeck coefficient obtained at room temperature is 290 µV/K and the figure of merit with κℓ = 0 is 0.98. The density functional perturbation theory (DFPT) is used to calculate the 2nd order harmonic and 3rd order anharmonic force constants. The phonon dispersion and density of states are computed from the 2nd order harmonic force constants using Phonopy code. The lattice thermal conductivity and other lattice dependent transport properties are calculated using both the harmonic and anharmonic force constants via ShengBTE program. The specific heat and lattice thermal conductivity at room temperature is 305.5 J/mol K and 1.35 × 10−3 W/m K, respectively. The figure of merit ZT for β-SiTe at room temperature using the κℓ obtained from ShengBTE is 0.78 at 800k.