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MM: Fachverband Metall- und Materialphysik
MM 19: Methods in Computational Materials Modelling I: Materials Design
MM 19.3: Vortrag
Dienstag, 17. März 2015, 10:45–11:00, H 0106
Accurate Thermal Conductivities from First Principles — •Christian Carbogno and Matthias Scheffler — Fritz-Haber-Institut der MPG, Berlin
In spite of significant research efforts, a first-principles determination of the thermal conductivity at high temperatures has remained elusive. Boltzmann transport techniques that account for anharmonic effects only perturbatively become inaccurate or inapplicable under such conditions; non-equilibrium molecular dynamics (MD) methods suffer from enormous finite-size artifacts in the computationally feasible supercells. Using Green-Kubo theory [1], we overcome this limitation by performing equilibrium ab initio MD simulations, from which the thermal conductivity is assessed from the auto-correlation function of the heat flux (including anharmonic effects to all orders). Foremost, we introduce and discuss a first-principles definition of the heat flux using the virial theorem. We validate our approach and in particular the techniques developed to overcome finite time and size effects, e.g., by inspecting silicon, the thermal conductivity of which is particularly challenging to converge [2]. Furthermore, we investigate the thermal conductivity of ZrO2, which is known for its high degree of anharmonicity. Our calculations shed light on the heat resistance mechanism active in this material, which eventually allows us to discuss how the thermal conductivity can be controlled by doping [3].
[1] R. Kubo, et al., J. Phys. Soc. Jpn. 12, 1203 (1957).
[2] Y. He et al., Phys. Chem. Chem. Phys. 14, 16209 (2012).
[3] C. Carbogno, et al., Phys. Rev. B 90, 144109 (2014).