Thermoelectric Properties of p-Type Cu₂O, CuO, and NiO from Hybrid Density Functional Theory

The electronic transport coefficients of three Earth-abundant metal oxides Cu₂O, CuO, and NiO were investigated using hybrid density functional theory (DFT). Hybrid DFT methods combined with local Gaussian-type basis sets enabled band structure studies on both non-magnetic and magnetic p-type metal oxides without empirical corrections. The CRYSTAL code was used for obtaining the wavefunction, and the transport properties were calculated with two different methodologies to benchmark their accuracy: a numerical approach as implemented in the BoltzTraP code and an analytical approach recently implemented in CRYSTAL17. Both computational methods produce identical results in good agreement with experimental measurements of the Seebeck coefficient. The predicted electrical conductivities are overestimated, owing likely to the used approximation of a constant electronic relaxation time in the calculations, as explicit electron scattering is neglected and relaxation time is considered only as a free parameter. The obtained results enable us to critically review and complement the available theoretical and experimental literature on the studied p-type thermoelectric metal oxide materials.