Size dependent thermal conductivity of single-walled carbon nanotubes

In this paper, we report a non-equilibrium molecular dynamics study on the size-dependent thermal conductivity in single-walled carbon nanotubes with lengths up to micrometers at room temperature. It is found that the size-dependent thermal conductivity of single-walled carbon nanotubes can be described by κ (L, d) ≈ κ g (L) (1 e ^- 0.185 d /a ₀), where L is the tube length, d is the diameter, a 0 2.46 Å is the graphene lattice constant, and κ _g (L) ∞ L ^α is the thermal conductivity of a graphene of length L. In the above, α 1 for L < l ₀, and α ∼ 0.21 for L > l ₀, independent of the tube chirality (zigzag or armchair), where l ₀ ≈ 200 nm and 300 nm are the effective phonon mean free path for zigzag and armchair tubes, respectively. Physical interpretations of such geometry dependence are provided in the paper by analyzing the spectral energy density, the dispersion relationship, the phonon density of state, and the power spectrum of phonons.