Thermoelectric property of (Ca,M)TiO3 by ab initio calculation

We study the thermoelectric property of CaTiO₃ by electronic structure calculations. CaTiO₃ is an insulator with a high band gap possessing low electrical and thermal conductivity. The DV-X a (discrete variational-X a) method is used. The calculation needs atomic number, position of atoms, kind of atoms and symmetry data for the cluster. We calculated the perovskite type of calcium titanate (CaTiO₃). This cluster, with transition metal-additions (Ca,M)TiO₃ forms p-type and n-type semiconductors possessing impurity energy levels of the donor and acceptor between the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital). We assumed the Seebeck coefficient depends on the energy gap based on the computer simulation of Sugihara et al. (1999). We substituted Sr and Nb for Ti in CaTiO₃ and the Seebeck coefficient was calculated from HOMO, LUMO level and the impurity levels. Then the Seebeck coefficient at 500 K was calculated to be 7166 μ V/K for CaTiO₃, 1806 μ V/K for Nb-added CaTiO₃ and 896 μ V/K for Sr-added CaTiO₃, respectively