The first principles calculations on the thermoelectric properties of Bulk Au 2 S with ultra-low lattice thermal conductivity

Sulfide nanocrystals and their composites have shown great potential in the thermoelectric (TE) field due to their extremely low thermal conductivity. Recently a solid and hollow metastable Au2S nanocrystalline has been successfully synthesized. Herein, we study the TE properties of this bulk Au2S by first-principles calculations and semiclassical Boltzmann transport theory, which provided the basis for its further experimental studies. Our results indicate that the highly twofold degeneracy of the bands appear at the Γ point in Brillouin zone, resulting in a high Seebeck coefficient. Besides, Au2S exhibits an ultra-low lattice thermal conductivity (~0.88 Wm-1K-1 at 700 K). At 700 K, the ZT value of the optimal p-type doping was close to 1.76, which was higher than 0.8 of ZrSb at 700 K and 1.4 of PtTe at 750 K. Our work clearly demonstrates the advantages of Au2S as a TE material and would greatly inspire further experimental studies and verifications.