Fig. 1. (a) Crystal structure of bulk Au₂S (Au: orange; S: yellow). (b) Total and partial densities of states and band structure of Au₂S calculated with PBE. The Fermi level is set at zero.

Fig. 2. Free energy fluctuation and the final structure of Au₂S in AIMD simulations at 300 K, 500 K, and 700 K.

Fig. 3. The RDF of Au₂S at 300 K, 500 K, and 700 K.

Fig. 4. (a) Seebeck coefficients, (b) electrical conductivity, (c) electronic thermal conductivity, and (d) power factor with respect to the scattering time as functions of the chemical potential μ.

Fig. 5. (a) Phonon dispersion and corresponding total and partial phonon density of states of Au₂S. (b) Calculated lattice thermal conductivity with respect to temperature for Au₂S.

Fig. 6. (a) Phonon group velocities, (b) Grüneisen parameters, (c) phonon relaxation time, and (d) P₃ phase space with respect to frequency for Au₂S.

Fig. 7. The thermoelectric figure of merit as a function of (a) chemical potential and (b) carrier concentration for Au₂S at 300 K, 500 K and 700 K.