Perex
Abstract:
This talk aims to provide an overview of modelling thermoelectric materials by local-density approximation and dynamical mean field method (LDA+DMFT). After an explanatory introduction including a description of Kubo’s formula for the thermopower, the method is illustrated by two examples: In NaxCoO2, the combined effects of electronic correlation and disorder are studied in detail. To account for the stoichiometric factor x, an expansion of standard DMFT to include disorder by means of the coherent potential approximation (CPA) has been applied.
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For NaxCoO2, the large thermopower at room temperature can be explained by an electron-hole asymmetry which is enhanced by the combination of disorder and correlation. The second exemplary compound is FeSb2 showing a colossal thermopower at low temperature. The electronic structure of this material is much more complicated than in the case of sodium cobaltate - especially the strong d-p hybridization leads to effects which are not fully understood so far.