Anharmonicity in Thermal Insulators: An Analysis from First Principles

• The anharmonicity of atomic motion limits the thermal conductivity in crystalline solids. However, amicroscopic 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 fullyanharmonic ab initio Green-Kubo calculations for 58 of them, finding 28 thermal insulators withκ < 10 W=mK including 6 with ultralow κ ≲ 1 W=mK. Our analysis reveals that the underlying stronganharmonic dynamics is driven by the exploration of metastable intrinsic defect geometries. This is atvariance with the frequently applied perturbative approach, in which the dynamics is assumed to evolvearound a single stable geometry.

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NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

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