Influence of the relaxation time approximation on first principle study of transport coefficients in thermoelectric material PbTe

The present master thesis consists in a study of the influence of the relaxation time approximation in the ab-inito computation of the thermoelectric properties of lead telluride. The calculations are performed in the framework of the Boltzmann Transport Equation using the ab-initio computed band structure as starting point. Different models for the relaxation times due to phonon scattering are tested, from a very simple constant one to energy and temperature dependent relaxation times. The resulting transport coefficients are compared to experimental measurements in order to check the accuracy of the different models.