Regensburg 2007 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 20: Poster session
MM 20.51: Poster
Dienstag, 27. März 2007, 14:45–18:00, Poster C
Calculation of transport coefficients from ab-initio methods — •Laurent Chaput1,2, Pierre Pecheur1, and Hubert Scherrer1 — 1Laboratoire de Physique des Matériaux, Nancy, France — 2Institut für Festkörperforschung, Forschungszentrum Jülich, Germany
A module to calculate transport properties of thermoelectric materials has been implemented. The system response is described within the framework of Boltzmann transport theory and the electronic structure of the system is taken as the one of Kohn-Sham electrons. This way we obtain the Onsager coefficients from which the thermoelectric tensor, the Hall tensor and the Lorenz coefficient are calculated. These quantities depend crucially on electron velocities. These are calculated using the spectral differentiation method. Therefore we obtain a very high accuracy while keeping the time-cost of the method relatively low. The other advantage of this method is that it is independent of the basis used for the electronic structure calculation. The module can therefore be used with a variety of methods. In this contribution we consider the peculiar dependence with respect to temperature of the thermoelectric power of the MAX phase Ti3SiC2 . It has been reported to be essentially zero. The calculation of the thermoelectric tensor show that this come from a compensation between the components of the thermoelectric tensor. They are positive in the basal plane and negative along the z axis. We also derive a sum rule for the relaxation time. This simplify the calculation of the Hall tensor.