We have investigated the length dependence of (10,10) carbon nanotube thermal conductivity using molecular dynamics simulations. This work has made several important contributions, including 1) the first quantum correction of molecular dynamics thermal conductivity results for carbon nanotubes, which is essential for modeling the thermal conductivity temperature dependence appropriately; 2) a new technique for determining whether transport is ballistic or diffusive, based on heat current autocorrelation decay times; 3) a new, simple technique for estimating average speed of sound from molecular dynamics without the need for complicated dispersion relation calculations; and 4) a new method for eliminating size effects from molecular dynamics thermal conductivity calculations even for domain sizes much smaller than the bulk phonon mean free path.

We have investigated the diameter dependence of the thermal conductivity of silicon nanowires using Monte Carlo simulations. We have observed that thermal conductivity decreases as nanowire diameter decreases. By comparison to experimental measurements, we have also found that confinement effects on the dispersion relation of silicon nanowires are important at diameters smaller than 100 nanometers.