Why does PbTe Show Opposite Trend in Electrical Conductivity vs. Temperature to Data Found In Literature?

Hello,

In the paper "Model of Transport Properties of Thermoelectric Nanocomposite Materials" 2009 it was found that PbTe with no impurities had an exponentially increasing electrical conductivity on the temperature range of 25 to 300 Kelvin for carrier concentrations of ~6e8 cm^-3. However, when I use the default settings for this simulation I observe the opposite trend of exponential decrease. Is it possible to change the parameters in the simulation to match the paper's results? The paper uses a non-parabolic Kane dispersion relation and expressions for the scattering time which are put into differential conductivity integrals, which as I understand come from the same linearized Boltzmann transport equation that is in this simulation tool. The only explicitly shared parameter is density which is 8.24e3 in this tool and 8.16e3 in the paper and I set the simulation carrier concentration to that in the paper. (Also, the paper includes the difference in reciprocal static and dynamic dielectric constants in terms of the band gap energy in an equation that doesn't appear to be dimensionally consistent.)

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David Bernd Ollodart@ onThe paper I cited fabricated PbTe from nanoparticles so there existed grain boundaries not present in bulk material. These grain boundaries are significant, being modeled in the paper as rectangular energy barriers of 60 meV on the temperature range of 0 K < T < 300 K (the energy of Brownian motion at T = 300 K is approximately k_B * T = 25 meV, the electrons can move because of quantum tunneling through barrier). Therefore as opposed to bulk materials there is an increase in the electrical conductivity and mobility with temperature.

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