Predicted thermoelectric properties of natural superlattice structural compounds BaCuChF (Ch = S, Se and Te) by first-principles calculations

The electronic structures of BaCuChF (Ch = S, Se and Te) are investigated using first-principles calculations. It is found that the band structures exhibit relatively large dispersion around the valence band maximum in the Γ-M and Γ-X directions while rather flat in the Γ-Z direction, and the upper valence bands consist of Cu−Ch antibonding states which determine the transport properties of p-type BaCuChF. The transport properties of p-type BaCuChF (Ch = S, Se, and Te) have been estimated based on semi-classical Boltzmann transport theory. It is observed that they possess high Seebeck coefficient which originate from the quasi-flat nature of these bands at the valence band edges, and they show a prominently anisotropic nature in electrical conductivity which attribute to their naturally layered structures. The optimal doping concentrations have been estimated based on the predicted maximum power factors. According to these results, natural superlattice structural compounds BaCuChF are expected to possess promising thermoelectric performance and worth exploration in experiment.