Thermal transport of bilayer graphene: a homogeneous nonequilibrium molecular dynamics study

In this paper, the thermal transport of bilayer graphene is revisited by the homogeneous nonequilibrium molecular dynamics (HNEMD) method realized in a graphics processing unit based molecular dynamics package, GPUMD. Our simulations are carried out in three-dimensional boxes. An optimized Teroff potential is used to describe C-C covalent bonds, and the inter-layer van der Waals interaction is described by the 12-6 Lennard-Jones potential. Since the HNEMD method is homogeneous without boundary scattering, we obtain more accurate results than previous nonequilibrium molecular dynamics studies. Through intensive simulations, the main findings of the paper are as follows. (1) We find an efficient simulation setting, yielding results which are in good agreement with the experimental data; (2) Although the increase of the system size and the extension of production period has a beneficial effect to obtain more convergent results, these lead to large discrepancy with the experimental data; (3) The thermal conductivity is reduced by the phonon scattering among graphene layers; (4) The spectral decomposition of thermal conductivity shows that the bilayer graphene retains the spectrum of its monolayer counterpart except for the increasing magnitudes; (5) The spectral phonon mean free path of bilayer graphene reveals the presence of a new phonon mode which may have a negative contribution to the thermal conductivity.