Three-Particle Correlations in Simple Liquids

TL;DR

This study employs video microscopy to analyze three-particle correlations in a 2D colloidal liquid, revealing local ordering near the fluid-solid transition and emphasizing the importance of triplet correlations for satisfying the Born-Green equation.

Contribution

It demonstrates the direct measurement of three-point correlations in a colloidal liquid and highlights their role in local ordering and theoretical consistency.

Findings

Triplet correlations increase near the fluid-solid transition.

Full triplet correlation functions are necessary for the Born-Green equation.

Superposition approximations fail to capture triplet correlations in strongly interacting systems.

Abstract

We use video microscopy to follow the phase-space trajectory of a two-dimensional colloidal model liquid and calculate three-point correlation functions from the measured particle configurations. Approaching the fluid-solid transition by increasing the strength of the pair-interaction potential, one observes the gradual formation of a crystal-like local order due to triplet correlations, while being still deep inside the fluid phase. Furthermore, we show that in a strongly interacting system the Born-Green equation can be satisfied only with the full triplet correlation function but not with three-body distribution functions obtained from superposing pair-correlations (Kirkwood superposition approximation).