Dresden 2014 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 49: Energy materials: Thermoelectrics

HL 49.6: Talk

Tuesday, April 1, 2014, 15:15–15:30, POT 051

Thermoelectric Coefficients from First Principles — •Karsten Rasim, Christian Carbogno, and Matthias Scheffler — Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin, Germany

In spite of significant efforts, an accurate assessment of the electronic transport coefficients, i.e., the electrical conductivity σ, the Seebeck coefficient S and the electronic heat conductivity κ_el, still constitutes an open challenge for first-principles theory. Even the most involved approaches [1] treat the nuclear dynamics in the harmonic approximation and thus become inaccurate at elevated temperatures. To overcome this limitation, we use the Kubo-Greenwood formalism [2] to assess σ, S, and κ_el from the thermodynamic equilibrium fluctuations of the electronic structure and of its dipole transition matrix elements. Anharmonic effects in the nuclear motion are fully incorporated by the means of ab initio molecular dynamics. We discuss the details of our implementation and validate our approach by investigating various direct and indirect band gap semiconductors. Furthermore, we compute the temperature dependent electronic transport coefficients of borcarbides, a material class regarded as promising for thermoelectric applications. We demonstrate that in this case anharmonic effects are crucial to achieve a correct description of the transport coefficients.

[1] P. Boulet and M. J. Verstraete, Comp. Mat.Sci. 50, 3 (2001)

[2] B. Holst, M. French, and R. Redmer, Phys. Rev. B 83, 235120 (2011).