Molecular Dynamics Simulation of Thermal Properties of Single Walled Carbon Nanotubes

Molecular dynamics (MD) simulations are a powerful tool for investigating the thermal behavior of carbon nanotubes (CNTs), which are renowned for their exceptional thermal conductivity and potential in nanoscale thermal management applications. This study employs the open-source software LAMMPS, in conjunction with VMD for model generation, to explore the thermal transport properties of (10,10) single-walled carbon nanotubes (SWCNTs) using non-equilibrium molecular dynamics (NEMD). The thermal conductivity of SWCNTs was evaluated across four tube lengths (5 nm, 10 nm, 20 nm, and 40 nm) and at temperatures ranging from 300 K to 600 K under two distinct boundary conditions: free boundary conditions (FBC) and periodic boundary conditions (PBC). Simulations utilized the AIREBO potential and Langevin thermostats, with parameters carefully selected to mirror realistic physical behavior and ensure steady-state temperature gradients. Results demonstrate a strong dependence of thermal conductivity on both tube length and boundary treatment. A power-law scaling relationship K(L) ∝ L^α was observed, with exponents ranging from approximately 0.6 to 0.78, indicating a transition from ballistic to diffusive phonon transport. Thermal conductivity ranged from ~800 W/m·K to ~10,800 W/m·K, with PBC cases yielding significantly higher values due to the absence of boundary scattering. These findings show good agreement with previously published simulations and align with the upper bounds of experimental measurements. This work provides a detailed and systematic analysis of phonon-mediated heat conduction in low-dimensional systems and is among the few studies to directly compare FBC and PBC under otherwise identical conditions. The insights gained are relevant for the development of CNT-based thermal interface materials and for advancing nanoscale heat dissipation strategies in high-performance electronics.