Electronic structure and related optical, thermoelectric and dynamical properties of Lilianite-type Pb7Bi4Se13: Ab-initio and Boltzmann transport theory

Abstract

The electronic, optical, thermoelectric, and dynamic properties of Pb 7 Bi 4 Se 13 have been investigated using first principles calculations. The existence of heavy elements, bismuth and lead, has required to consider the spin–orbit coupling as implemented in the second variational procedure. It was observed that the upper of the valence band region appears predominantly from Se-p states with an admixture of Bi- p and Pb- p states, while the CBM comes mainly from Bi- p states only. The calculated optical properties illustrate a small manifold direct and indi- rect inter-band transitions emerging in the visible region. Semi classic Boltzmann theory was then employed to determine the Seebeck coefficient, electrical conductivity, thermal conductivity, and power factor. The phonon dispersion curve has been computed and explained. It can be deduced that the slight structural instability ob- served from phonon calculations is related to lower lattice thermal conductivity. Our findings were compared with the available experimental measurements, showing a good agreement.