# Density fluctuations and random walks in an overdamped and supercooled simple liquid

## TL;DR

This paper investigates the short-time dynamics of a simple liquid, focusing on how density fluctuations influence particle motion, and provides analytical and numerical insights into diffusion behavior in supercooled and overdamped states.

## Contribution

It offers a combined analytical and numerical analysis of density fluctuations and particle diffusion in a Lennard-Jones liquid, linking microscopic behavior to macroscopic diffusion coefficients.

## Key findings

- Analytical expression matches experimental diffusion data for liquid argon.
- Density fluctuations are key to understanding reduced particle mobility.
- Behavior is similar in supercooled and overdamped regimes.

## Abstract

In this work, the short-time dynamics of simple liquid is explored both analytically and numerically with the focus on the interplay between the density fluctuations in a volume surrounding a chosen particle and its random walk motion. The particles interact via the Lennard-Jones potential with parameters corresponding to liquid argon. For large times, analytical calculations based on the fluctuation theory provides an explicit expression reproducing isothermal change of the self-diffusion coefficient in liquid argon corresponding to the experimental data. These results lead to the conclusion that such behavior is based on the reduced mobility of particles reflected in their density fluctuations that can be equivalently achieved in the cases of either low temperatures and pressures (supercooling) or moderate temperatures and high pressures (overdamping).