C117 炭素ナノチューブの熱伝導に関する分子動力学(新技術フォーラム-1 : 熱工学における量子力学)

Abstract

The heat conduction in finite length single walled carbon nanotubes (SWNTs) was simulated by the molecular dynamics method with the Tersoff-Brenner bond order potential. Temperature at each end of a SWNT was controlled by the phantom technique, and the thermal conductivity was calculated from the measured temperature gradient and the energy budgets in phantom molecules. The thermal conductivity was measured for two different diameter SWNTs with various lengths from 3 nm through 200 nm. Since the photon mean free path is estimated as order of lOOnm〜1μm, heat conduction of nanotubes with less than 1μm length should have the nearly 'ballistic' features with much less apparent thermal conductivity than infinitely long nanotubes. The Fourier's law of heat conduction may not be obeyed for these almost one-dimensional materials when rather high heat-flux conditions. The measured thermal conductivity did not converge to a finite value with increase in tube length, but an interesting power law relation was observed. The basic heat conduction mechanism was explored through the phonon dynamics extracted from the molecular dynamics simulations. The phonon density of states and photon dispersion relations were directly calculated from the simulated results.