Thermal transport from first principles beyond phonons

We present a systematic and numerically precise first-principles search for thermal insulators in material space. Using the high-throughput framework FHI-vibes [1] and a recently developed measure for the strength of anharmonicity [2], we first screen over thousands of materials, including complex oxides, chalcogenides, and ternary perovskites, to single out dozens of strongly anharmonic systems with potential for ultra-low thermal conductivity κ. We then perform ab initio Green-Kubo simulations on these candidates to accurately determine κ [3], thereby naturally including anharmonic effects and dynamical processes that cannot be described in a phonon picture, e.g., short-lived metastable configurations and structural phase transitions. We quantify and discuss the importance of such strong anharmonic effects on thermal transport across material space, and highlight systems for which perturbative approaches break down.

[1] https://vibes.fhi-berlin.mpg.de/
[2] F. Knoop, et al., Phys. Rev. Materials 4, 083809 (2020)
[3] C. Carbogno, R. Ramprasad, and M. Scheffler, Phys. Rev. Lett. 118, 175901 (2017)