Predicting the Phonon Properties of Carbon Nanotubes Using the Spectra Energy Density

Thermal transport by phonons in water/carbon nanotube (CNT) composite systems is investigated using molecular dynamics (MD) simulation. We calculate the spectral energy density of empty and water-filled CNTs and use it to extract the mode-specific phonon group velocities, relaxation times, and thermal conductivities. The total thermal conductivity predicted from the spectral energy density is consistent with what we predict using a direct application of the Fourier law in an MD simulation. The number of atoms and simulation runtime required to predict the spectral energy density, however, are both at least one order-of-magnitude smaller.