Thermal resistivity of Si-Ge alloys by molecular-dynamics simulation

We explore the ability of molecular-dynamics simulation to elucidate thermal transport in Si-Ge alloys. Simulations using Stillinger-Weber potentials yield values for the thermal resistivity significantly higher than experimental measurements. In agreement with experiment and theoretical predictions, we find that scattering from mass disorder is dominant, with bond disorder and strain effects playing a very minor role. To explore the origins of the large discrepancies with experiment, we use theoretical methods suitable for the limit where point-defect scattering dominates the resistivity. We find that point-defect scattering models based on a Debye spectrum cannot be used to fit our simulations, indicating that high-frequency modes may play an important role in the simulation. The results have important implications for using classical molecular-dynamics simulation to predict properties of alloy materials near and below the Debye temperature