  Based on first-principles calculations, we study the origin of the large
thermopower in Ni-doped LaRhO3 and Mg-doped CuRhO2. We calculate the band
structure and construct the maximally localized Wannier functions from which a
tight binding Hamiltonian is obtained. The Seebeck coefficient is calculated
within the Boltzmann's equation approach using this effective Hamiltonian. For
LaRhO3, we find that the Seebeck coefficient remains nearly constant within a
large hole concentration range, which is consistent with the experimental
observation. For CuRhO2, the overall temperature dependence of the calculated
Seebeck coefficient is in excellent agreement with the experiment. The origin
of the large thermopower is discussed.
