Molecular dynamics study on a nonequilibrium motion of a colloidal particle driven by an external torque

TL;DR

This study uses molecular dynamics simulations to analyze the nonequilibrium motion of a colloidal particle driven by an external torque, confirming the fluctuation theorem and aligning with Langevin equation results.

Contribution

It introduces a molecular dynamics approach that mimics experimental conditions more realistically for studying driven colloidal particles out of equilibrium.

Findings

Confirmed the fluctuation theorem for work production.

Results agree with Langevin equation simulations.

Provided detailed analysis of nonequilibrium fluctuations.

Abstract

We investigate the motion of a colloidal particle driven out of equilibrium by an external torque. We use the molecular dynamics simulation that is alternative to the numerical integration approach based on the Langevin equation and is expected to mimic an experiment more realistically. We choose a heat bath composed of thousands of particles interacting to each other through the Lennard-Jones potential and impose the Langevin thermostat to maintain it in equilibrium. We prepare a single colloidal particle to interact with the particles of the heat bath also by the Lennard-Jones potential while any dissipative force and noise are not employed. We prepare the simulation protocol fit to the overdamped limit in real experiments by increasing the size and mass of the colloidal particle. We study the stochastic properties of the nonequilibrium fluctuations for work and heat produced incessantly in time. We accurately confirm the fluctuation theorem for the work production. We show our results to agree accurately with those from the numerical integration of the Langevin equation.