Koh Heeyuen, Chiashi Shohei, Shiomi Junichiro, Maruyama Shigeo
Mechanical and Aerospace Engineering Department, Seoul National University, 1 Gwanak-ro, Gwanak-gu, Seoul, 08826, South Korea.
Department of Mechanical Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
Sci Rep. 2021 Jan 12;11(1):563. doi: 10.1038/s41598-020-79200-6.
Second sound and heat diffusion in single-walled carbon nanotubes (SWCNT) are well-known phenomena which is related to the high thermal conductivity of this material. In this paper, we have shown that the heat diffusion along the tube axis affects the macroscopic motion of SWCNT and adapting this phenomena to coarse-grained (CG) model can improve the precision of the coarse-grained molecular dynamics (CGMD) exceptionally. The nonlinear macroscopic motion of SWCNT in the free thermal vibration condition in adiabatic environment is demonstrated in the most simplified version of CG modeling as maintaining finite temperature and total energy with suggested dissipation process derived from internal heat diffusion. The internal heat diffusion related to the cross correlated momentum from different potential energy functions is considered, and it can reproduce the nonlinear dynamic nature of SWCNTs without external thermostatting in CG model. Memory effect and thermostat with random noise distribution are not included, and the effect of heat diffusion on memory effect is quantified through Mori-Zwanzig formalism. This diffusion shows perfect syncronization of the motion between that of CGMD and MD simulation, which is started with initial conditions from the molecular dynamics (MD) simulation. The heat diffusion related to this process has shown the same dispersive characteristics to second wave in SWCNT. This replication with good precision indicates that the internal heat diffusion process is the essential cause of the nonlinearity of the tube. The nonlinear dynamic characteristics from the various scale of simple beads systems are examined with expanding its time step and node length.
单壁碳纳米管（SWCNT）中的第二声和热扩散是众所周知的现象，这与该材料的高导热性有关。在本文中，我们表明沿管轴的热扩散会影响SWCNT的宏观运动，并且将这种现象应用于粗粒化（CG）模型可以极大地提高粗粒化分子动力学（CGMD）的精度。在绝热环境下自由热振动条件下SWCNT的非线性宏观运动，在CG建模的最简化版本中得到了证明，即通过从内部热扩散导出的建议耗散过程来维持有限温度和总能量。考虑了与来自不同势能函数的交叉相关动量相关的内部热扩散，并且它可以在CG模型中无需外部恒温的情况下再现SWCNT的非线性动态性质。不包括记忆效应和具有随机噪声分布的恒温器，并且通过Mori-Zwanzig形式主义量化热扩散对记忆效应的影响。这种扩散显示了CGMD和MD模拟之间运动的完美同步，其从分子动力学（MD）模拟的初始条件开始。与该过程相关的热扩散对SWCNT中的第二波显示出相同的色散特性。这种高精度的复制表明内部热扩散过程是管非线性的根本原因。通过扩大其时间步长和节点长度，研究了各种尺度的简单珠子系统的非线性动态特性。
