Anharmonicity in Thermal Insulators: An Analysis from First Principles

Understand

The anharmonicity of atomic motion limits the thermal conductivity in crystalline solids.

• However, a microscopic understanding of the mechanisms active in strong thermal insulators is lacking.
• In this letter, we classify 465 experimentally known materials with respect to their anharmonicity and perform fully anharmonic ab initio Green-Kubo calculations for 58 of them, finding 28 thermal insulators with $\kappa < 10$ W/mK including 6 with ultralow $\kappa \lesssim 1$ W/mK.
• Our analysis reveals that the underlying strong anharmonic dynamics is driven by the exploration of meta-stable intrinsic defect geometries.