Thermal conductivity in intermetallic clathrates: A first-principles perspective
Journal article, 2019

Inorganic clathrates such as Ba8GaxGe46-x and Ba8AlxSi46-x commonly exhibit very low thermal conductivities. A quantitative computational description of this important property has proven difficult, in part due to the large unit cell, the role of disorder, and the fact that both electronic carriers and phonons contribute to transport. Here, we conduct a systematic analysis of the temperature and composition dependence of low-frequency modes associated with guest species in Ba8GaxGe46-x and Ba8AlxSi46-x ("rattler modes"), as well as thermal transport in stoichiometric Ba8Ga16Ge30. To this end, we account for phonon-phonon interactions by means of temperature-dependent effective interatomic force constants, which we find to be crucial in order to achieve an accurate description of the lattice part of the thermal conductivity. While the analysis of the thermal conductivity is often largely focused on the rattler modes, here it is shown that at room temperatures modes with ω 10meV account for 50% of lattice heat transport. Finally, the electronic contribution to the thermal conductivity is computed, which shows the Wiedemann-Franz law to be only approximately fulfilled. As a result, it is crucial to employ the correct prefactor when separating electronic and lattice contributions for experimental data.

Author

Daniel Lindroth

Chalmers, Physics, Materials and Surface Theory

Joakim Brorsson

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Applied Surface Chemistry

Erik Fransson

Chalmers, Physics, Materials and Surface Theory

Fredrik Eriksson

Chalmers, Physics, Materials and Surface Theory

Anders Palmqvist

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry, Applied Surface Chemistry

Paul Erhart

Chalmers, Physics, Materials and Surface Theory

Physical Review B

24699950 (ISSN) 24699969 (eISSN)

Vol. 100 4 045206

Subject Categories

Ceramics

Other Physics Topics

Condensed Matter Physics

DOI

10.1103/PhysRevB.100.045206

More information

Latest update

11/7/2019