Equilibrium molecular dynamics simulations for the thermal conductivity of Si/Ge nanocomposites

摘要

Various methods have been used to study the thermal conductivity of nanocomposites which are playing increasing roles in energy conversion and thermal management. However, when the size of particle inclusions is on the order of several nanometers, the existing macro- and meso-scale analytical methods cannot be used to predict the thermal conductivity of nanocomposites due to the existence of both phonon wave interference and particle scattering effects. In this study, equilibrium molecular dynamics (EMD) is explored to study the thermal conductivity of Si/Ge nanocomposites. We found that EMD can be used to study the thermal conductivity of nanocomposites when multiple nanoparticles are included to avoid the artificial effect of simulation domain sizes. We then calculated the thermal conductivity of Si/Ge nanocomposites with different volumetric ratio and particle size at 300 K. The result shows that the thermal conductivity of Si/Ge nanocomposites first decreases and then increases with decreasing particle size at fixed volumetric ratio. The decreasing thermal conductivity is due to the increased phonon scattering at high surface to volumetric ratio. When the particle size is further reduced, the thermal conductivity recovers due to the phonon wave interference effect. The effect of particle shape on the thermal conductivity of Si/Ge nanocomposites is also studied.