Characterization of Analytical Thermal Conductivity Models Through Assesment Against Experiment and Simulation

The Klemens/Callaway equations [Phys Rev 119 (2), 507-509 (1960)] model lattice thermal conductivity (κ_L ) versus temperature and impurity concentration. This framework highlights the dominant phonon scattering mechanisms in a system, and is used for routine interpretation of experimental trends. The model predictions are often regarded as rough estimates due to the assumption of a monatomic lattice and Debye model dispersion. In this study, the Klemens model is applied to both experimental measurements and first-principles simulations of κ_L, where imperfections are introduced to scatter phonons. We demonstrate the proper application of this model to materials with complex unit cells, and resolve discrepancies over model inputs that can yield a factor of 2-10 difference in the predicted κ_L values. Additionally, the model is demonstrated to provide robust predictions of point defect scattering strength in a wide range of materials, whose dispersion relations are known to deviate significantly from the Debye model. We demonstrate how the dispersion relation dependence of the model is, in practice, lifted, allowing for surprising agreement between analytical theory and experiment. Thus, we provide justification for using this model on systems with arbitrary dispersion relations.