Low-Temperature Thermal Conductivity of Short Single-Walled Carbon Nanotubes Using a Modified Nosé-Hoover Thermostat

Abstract

The study aims at predicting the low-temperature thermal conductivity of short single-walled carbon nanotubes (SWCNTs) through a modified Nosé-Hoover (NH) thermostat method incorporated with nonequilibrium molecular dynamics (NEMD) simulation. The thermostat method accounts for the phonon effects by virtue of the lattice vibrational and zero-point energy to accurately capture the quantum effects at temperatures below Debye temperature. Using this method, the dependences of the tube length, diameter, chirality, and temperature on thermal conductivity are examined, and the size-dependent phonon transport phenomena in the SWCNTs are also studied. The effectiveness of the proposed model is demonstrated through comparison with the results of the standard NH- and “massive” NH chain (MNHC)-based NEMD models with or without quantum corrections as well as the literature experimental and theoretical data. The results showed that the proposed model is the only one among those five that allows better agreement with the published experimental and theoretical predictions as well as the T ^λ-dependence (λ = 2–3) of thermal conductivity at low temperature due to the dominated phonon boundary scattering. Even with quantum corrections, by which the solution can be substantially improved, the standard NH- and MNHC-based models remain unable to follow the experimental data at temperatures below 300 K. Due to ballistic–diffusive phonon transport, the low-temperature thermal conductivity of SWCNTs with lengths greater than 5 nm shows strong dependence on tube's length, diameter, and chirality.

Keywords:

• thermal conductivity
• single-walled carbon nanotubes
• nonequilibrium molecular dynamics
• modified Nosé-Hoover (NH) thermostat

Acknowledgments

The work is partially supported by National Science Council, Taiwan, R.O.C., under grants NSC98-2221-E-007-016-MY3 and NSC100-2221-E-035-036-MY3.