Theoretical search for Chevrel-phase-based thermoelectric materials

We investigate the thermoelectric properties of some semiconducting Chevrel phases. Band-structure calculations are used to compute thermopowers and to estimate the effects of alloying and disorder on carrier mobility. Alloying on the Mo site with transition metals like Re, Ru, or Tc to reach a semiconducting composition causes large changes in the electronic structure at the Fermi level. Such alloys are thus expected to have low-carrier mobilities. Filling with transition metals was also found to be incompatible with high thermoelectric performance based on the calculated electronic structures. Filling with simple metals, like Zn, Cu, and especially with Li was found to be favorable. The calculated electronic structures of these filled Chevrel phases are consistent with low scattering of carriers by defects associated with the filling. We expect reasonable mobility and high thermopower in materials with compositions near $(\mathrm{L}\mathrm{i},\mathrm{C}\mathrm{u}{)}_4{\mathrm{Mo}}_6{\mathrm{Se}}_8.$