Spectral phonon transport properties of silicon based on molecular dynamics Simulations and lattice dynamics

Although the thermal conductivity of silicon has been studied before, current estimations for the phonon mean free paths have not provided full explanation of the strong size effects experimentally observed for various silicon micro and nanostructures. Since phonon relaxation time models are mostly semi-empirical, the mean free paths cannot be determined reliably and questions remain as to which polarizations, frequencies and wavelengths are dominant heat carriers. Here we have used a combination of equilibrium molecular dynamics simulations and lattice dynamics calculations to fully detail the spectral dependence of phonon transport properties in bulk silicon. By considering the frequency dependence of the specific heat, group velocities and mean free paths, we address these unresolved questions and examine the errors associated with isotropic and frequency averaged approximations. Simulation details, such as the convergence of results on the simulation time and extraction of phonon transport properties in different crystallographic directions, are also discussed.