Does equilibrium or nonequilibrium molecular dynamics correctly simulate thermal transport properties of carbon nanotubes?

Abstract

There has been a lot of debate on whether non-Fourier thermal conduction can be observed in quasi-one-dimensional materials such as carbon nanotubes (CNTs) and, additionally, whether the phenomenon can be found by equilibrium or nonequilibrium molecular dynamics (EMD or NEMD) simulations. In fact, so far EMD and NEMD simulations have revealed disparities of thermal transport in CNTs, ranging from purely diffusive behavior, to diffusive-ballistic transition, and to non-Fourier thermal conduction. By carefully examining the roles of interfacial thermal resistances and applied temperature differences in NEMD simulations, we show that the two effects often yield spurious results. After removing the unwanted effects that have been overlooked by previous works, we find that most EMD and NEMD simulations on CNTs consistently display diffusive thermal conduction for length (L) g 200 nm. The finding is further supported by the disappearance of nonlocal thermal conduction for L g 200 nm. Our results clarify many discrepancies of previous works and point out that nonideal thermostats commonly used in EMD and NEMD simulations would give an effective contact thermal resistance that misleads data interpretations. Overall, we find EMD and NEMD simulations conducted so far disagree with the current experimental results of nondiffusive thermal conduction in CNTs.