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

Area of Science:

• Physical Chemistry
• Condensed Matter Physics
• Statistical Mechanics

Background:

• Understanding short-time dynamics in simple liquids is crucial for molecular behavior.
• The interplay between density fluctuations and particle motion governs liquid properties.

Purpose of the Study:

• To investigate the short-time dynamics of simple liquids analytically and numerically.
• To explore the relationship between density fluctuations and random walk motion of particles.

Main Methods:

• Analytical calculations using fluctuation theory.
• Numerical simulations of particles interacting via the Lennard-Jones potential.
• Analysis of self-diffusion coefficient in liquid argon.

Main Results:

• An explicit expression for isothermal self-diffusion coefficient change was derived.
• The derived expression accurately reproduces experimental data for liquid argon.
• Particle mobility reduction due to density fluctuations was identified as key.

Conclusions:

• The study concludes that density fluctuations significantly impact particle mobility and self-diffusion.
• Reduced mobility, leading to changes in self-diffusion, can be achieved through supercooling or overdamping.
• The findings provide insights into the thermodynamic conditions affecting liquid dynamics.