Séminaire

Mardi 16 Janvier 2018 à 11h00.

Microscopic origin of anomalous thermal transport in intermetallic clathrates: A first-principles study

''Lattice thermal conductivity (LTC) of complex host-guest structures, such as clathrates and skutterudites, is unusually low (~ 1 W/mK) and sometimes shows glasslike temperature dependence. While the previous first-principles study has clarified that the rattling guest atoms cause the significant reduction in LTC by strongly enhancing the three-phonon Umklapp scattering rates [1], the atomistic origin of the anomalous temperature dependence still remains unclear. In particular, the roles of the strong quartic anharmonicity of rattlers, as well as the dynamical/static disorders, have never been investigated by first-principles calculations.
To elucidate the atomistic origin of the anomalous thermal conductivity in complex systems, we have recently investigated the role of the strong quartic anharmonicity of rattlers in lattice dynamics and thermal transport of type-I clathrate Ba8Ga16Ge30. We show that the inclusion of the effects of the quartic anharmonicity of rattling guest dramatically changes the temperature dependence of LTC, leading to an improved agreement with experimental results. We also discuss the role of disorders in LTC of clathrates. This talk is based on [2].
References:
[1] T. Tadano, Y. Gohda, and S. Tsuneyuki, Phys. Rev. Lett. 114, 095501 (2015).
[2] T. Tadano and S. Tsuneyuki, arXiv:1710.00311''