LDA+Ucalculation of electronic and thermoelectric properties of dopedCuCoO2

Abstract

Doped ${\mathrm{CuCoO}}_{2}$ is a candidate oxide material for thermoelectric power generation. The evolution of the band structure and thermoelectric properties of ${\mathrm{CuCoO}}_{2}$ upon hole and electron doping in the ${\mathrm{CoO}}_{2}$ layer and hole doping at the Cu site were calculated by the local-density approximation (LDA) and $\mathrm{LDA}+U$ methods and using standard Boltzmann theory. The doping was simulated by the virtual atom approximation and the supercell approach and the results were compared with previous calculations using the rigid band approximation. The calculated thermopowers are comparable for the virtual atom and rigid band approximations, but the thermopower obtained from the supercell calculation is significantly lower. The reason is the similar energy of Co and Cu $d$ orbitals and the hybridization of symmetrically related Co ${a}_{1g}$ and Cu ${d}_{{z}^{2}}$ orbitals. As a consequence, both cations contribute to the bands around the Fermi level and hence a substitution at any of the cation sites alters the band structure at ${E}_{F}$ and affects the thermoelectric properties. Our results show that in the case of hole doping, higher thermopower is obtained for substitution at the Cu site than in the ${\mathrm{CoO}}_{2}$ layer.