Phonon-mediated thermal transport: Confronting theory and microscopic simulation with experiment

We discuss recent advances in the microscopic simulations of thermal conductivity through the prism of comparisons with experimental measurements. By dissecting the thermal conductivity into its constituent properties, heat capacity, phonon structure and anharmonic phonon properties, we show that the reliable prediction of the thermal transport properties over a range of conditions requires each to be described correctly. However, it is sometimes possible to obtain thermal conductivity values in overall good agreement with experiment through a cancellation of errors in the constituent properties. Major advances in the prediction of thermal transport properties in the last few years have come through increases in computational power and through development of numerical algorithms for the essentially exact solution of the linearized Boltzmann Transport Equation, with interatomic interactions described by first-principles electronic-structure calculations. This approach enables consistent ab initio determination of the thermal conductivity in the pure crystals. We also discuss the effects of various defects on thermal conductivity and compare results from the atomistic simulations, classical theories from the 1950s, and experimental measurements.

► Thermal conductivity κ is an integral over phonon properties, including anharmonic properties.
► For pure crystals fully ab initio calculations of κ is now possible; excellent agreement with experiment.
► Defective systems remains a challenge, one has to relay on classical potentials.