# Molecular dynamics simulations of the rotational and translational diffusion of a Janus rod-shaped nanoparticle

## TL;DR

This study uses molecular dynamics simulations to analyze how Janus rod-shaped nanoparticles diffuse in a fluid, revealing that wettability contrast influences their rotational and translational diffusion behaviors.

## Contribution

It introduces a detailed MD simulation analysis of Janus rod-shaped nanoparticles, highlighting the effects of wettability contrast on their diffusion properties and orientation dynamics.

## Key findings

- Higher wettability contrast increases diffusion coefficients.
- Diffusion coefficients align with analytical predictions for uniform particles.
- Janus particles tend to rotate to minimize drag by orienting nonwetting sides along displacement.

## Abstract

The diffusion of a Janus rod-shaped nanoparticle in a dense Lennard-Jones fluid is studied using molecular dynamics (MD) simulations. The Janus particle is modeled as a rigid cylinder whose atoms on each half-side have different interaction energies with fluid molecules, thus comprising wetting and nonwetting surfaces. We found that both rotational and translational diffusion coefficients are larger for Janus particles with higher wettability contrast, and these values are bound between the two limiting cases of uniformly wetting and nonwetting particles. It was also shown that values of the diffusion coefficients for displacements parallel and perpendicular to the major axis of a uniformly wetting particle agree well with analytical predictions despite a finite slip at the particle surface present in MD simulations. It was further demonstrated that diffusion of Janus particles is markedly different from that of uniform particles; namely, Janus particles preferentially rotate and orient their nonwetting sides along the displacement vector to reduce drag. This correlation between translation and rotation is consistent with the previous results on diffusive dynamics of a spherical Janus particle with two hemispheres of different wettability.