Investigation of the thermal behaviors of folded graphene by non-equilibrium molecular dynamics simulation

The thermal conductivities (TCs) of graphene and folded graphene (FG) were calculated by non-equilibrium molecular dynamics (NEMD) simulation with the Condensed-phase Optimized Molecular Potential for Atom Simulation Studies (COMPASS) force field. The heat flux of FG model is along the direction perpendicular to the graphene sheet fragments connected by two nearest kinked regions. By extrapolation of the NEMD TC data in order to obtain the corresponding macroscopic TC values, the calculated graphene TC is about 2212 W/mK, which is located within the previous simulation data. For FG, the predicted TC value is about 71.4 W/mK, which is only 3.3% that of the graphene TC, indicating the TC of graphene can be effectively reduced by folding the graphene. The phonon vibrational spectrums of graphene and FG were also calculated by the Fourier transform of the velocity autocorrelation function. The spectrum ranging from 1150 to 1650 cm^-1 and at peaks of 620, 750, 1250, 1750 cm^-1 of graphene are higher than those of FG. The decrease of the amplitudes of the long-wave phonon mode is the main reason for the reduction in the TC of FG.