The disparate thermal conductivity of carbon nanotubes and diamond nanowires studied by atomistic simulation

Molecular dynamics simulations were used to calculate the thermal conductivity of carbon nanotubes and diamond nanowires with atomic interactions modeled by the Brenner potential The dependence of thermal conductivity on length, temperature, and temperature "boundary" condition was investigated. Lengths from 50 nm to 1 μm were simulated at a temperature of 290 K, and additional simulations were performed at 100 K and 400 K, for the 100 nm length. Thermal conductivity was found to be significantly suppressed for the shorter lengths. Two different artificial thermostats were used to impose the temperature difference: one rescaled velocities (the Berendsen thermostat), the other assigned velocities sampled from the appropriate Boltzmann distribution to randomly selected atoms for each numerical time step (the Andersen thermostat). Thus, the Berendsen thermostat amplifies existing atomic motions, while the Andersen thermostat, in a sense, disrupts the atomic motions. Nevertheless, results were very similar. All simulations were run for at least 200,000 time steps of 1 fsec each.