Session: 11-05-02: Thermophysical Properties: Characterization and Modeling Across Scales

Paper Number: 144537

144537 - Stochastic Thermodynamics for the Intra Molecular Damping and Thermal Conductivity of Swcnt 

As of Zwanzig’s nonlinear generalized Langevin equation[1], the memory effect is the term that explains the intercorrelation between the target system and the heat bath. When the system is simplified into two degrees of freedom(DOF) condition in an adiabatic environment, such as SWCNT or other quasi-one dimensional system regarded as a simple beads system, the strong coupling between each degree of freedom induces memory effects as that of the target system and heat bath. In accordance of Sekimoto’s derivation[2] on Langevin equation whose thermal fluctuation forms microscopic thermodynamics between the work from the random force and its internal energy, the energy released from the memory effect between DOFs are also considered to be under the similar thermodynamics regime. Few stochastic thermodynamics studies modeled the related condition for coarse grained(CG) particles, yet a quantitative analysis for the memory effect and entropy production has been in absent. The motion of of the quasi one dimensional system with the abundant DOF is known to cause a high thermal conductivity with the existence of the Z mode. The memory effect in the equation of motion without a simplification as Markovian regime, which is supposed to describe the most exact dynamic mechanism of thermal energy transport in the system, therefore, is the key to quantify the effect of Z mode or to reveal the hidden mechanism to induce ballistic transport in quasi-one dimensional system.

In 2021, Koh et al., has shown that the memory effect can be caused from the CG model of SWCNT between two DOFs. It is verified in the data set of molecular dynamics and Mori-Zwanzig formalism[3]. As for this cross-correlation, we supposed that it can be characterized as a temporal heat source that arouses heat diffusion as damping as newly suggested EOM of thermostat of CG particle.

 This assumption is adapted to coarse-grained model as the internal thermalization process into the equation of motion, and the trial advances the precision of the calculation of nonlinear dynamic characteristics of quasi one dimensional molecular system like SWCNT and DNA strands[3,4] without dissipated particle dynamics regime. As showing clear synchronization with the motion from the atomic scale molecular dynamics simulation, heat diffusion for cross correlation in single walled carbon nanotubes(SWCNT) with the temperature difference shows the spatiotemporal distribution with a clear wave packet traversing along the tube[5]. Unlike the pure soliton, it has multiple wave packets that start from both ends of SWCNT in non-equilibrium molecular dynamics (NEMD) simulation. Further study on the effect of the different aspect ratio and bundling condition of SWCNT in NEMD quantifies the amount of energy loaded on the wave packet from the heat diffusion of the cross correlated momentum and how it is affected by the interface.

The cross correlation in this scheme is the measure of the interdependency of the two Hamiltonians in the system which are translational and rotational motion of the lumped mass. The heat diffusion is intuitively regarded as a necessary process to conserve the energy and the independency of each Hamiltonian in coarse grained molecular dynamics system as decoupling the entangled states to satisfy Stackel condition[6] rather than a phenomenological truth in atomic scale system. To overcome this ambiguity as bolstering the observation of wave packet in NEMD, the validation of the phenomenon of heat diffusion for abnormality caused by cross correlation is conducted using stochastic thermodynamics[7] following Jarzynski’s frameworks[8] alongside its numerical assessment from the data in molecular dynamics. From this approach, the clear liaison between the heat diffusion and the cross correlation can be established as adapting Smoluchowski equation for the evolution of cross correlated state[9].

In this talk, we are going to introduce 1) how cross correlation in CG particles is validated as a diffusion process in the atomic scale phenomenon using stochastic thermodynamics, 2) the amount of the cross-correlated and diffused heat energy from NEMD of suspended SWCNT and 3) the change of cross-correlation on the interface of molecules in bundling.

 

[1] Zwanzig, J. Stat. Phys. 9, 3 (1973).

[2] Sekimoto, Prog. Theo. Phys. 130 (1998).

[3] Koh et al., Sci. Rep. 11, 1-14 (2021).

[4] Koh et al., arXiv:2397.04597 (2023).

[5] Koh and Maruyama, Proc. of SHTC2022 85796 (2022).

[6] Pars, Am. Math. Mon. 56, 6 (1949).

[7] Koh and Maruyama, arXiv:2401.13655 (2024).

[8] Jarzynski, Phy. Rev. X 011008 (2017).

[9] Zwanzig, R., Nonequilibrium Statistical Mechanics, Oxford University Press (2011).

 

Presenting Author: Heeyuen Koh Seoul National University

Presenting Author Biography: Postdoctoral Fellow/Researcher (2019-Present)
Research fields :
  - Nonlinear dynamics and nonequilibrium statistical mechanics in molecular system like SWCNT and
DNA including intramolecular energy transport
  - Thermalization in coarse grained molecular dynamics system
  - Neural network building for paramater optimization and functionals

EDUCATION
The University of Tokyo Tokyo, Japan
Doctor of Engineering, Department of Mechanical Eng. 2014
Dissertation - Modeling of Thermally Induced Vibration of Carbon Nanotubes
Advisor: Prof. Shigeo Maruyama
Research field - Nonlinear dynamics, Carbon nanotubes, MD and CGMD simulation

KAIST Dae-jeon, South Korea
M.S. Mechanical Engineering 2008
B.S. Mechanical Engineering 2006

Authors:

Heeyuen Koh Seoul National University
Shigeo Maruyama The Univ. of Tokyo