Static triplet correlations in glass-forming liquids: A molecular dynamics study

TL;DR

This study numerically analyzes static triplet correlations in glass-forming liquids, revealing structural differences between models and their potential impact on understanding the glass transition.

Contribution

It provides the first detailed comparison of three-point static correlations in Lennard-Jones and WCA models, linking structural features to dynamic behavior.

Findings

Lennard-Jones model shows more pronounced local ordering.

Structural differences are amplified at the triplet level.

Genuine three-body contributions are identified at small wave-vectors.

Abstract

We present a numerical evaluation of the three-point static correlations functions of the Kob-Andersen Lennard-Jones binary mixture and of its purely repulsive, Weeks-Chandler-Andersen variant. In the glassy regime, the two models possess a similar pair structure, yet their dynamics differ markedly. The static triplet correlation functions S^(3) indicate that the local ordering is more pronounced in the Lennard-Jones model, an observation consistent with its slower dynamics. A comparison of the direct triplet correlation functions c^(3) reveals that these structural differences are due, to a good extent, to an amplification of the small discrepancies observed at the pair level. We demonstrate the existence of a broad, positive peak at small wave-vectors and angles in c^(3). In this portion of k-space, slight, systematic differences between the models are observed, revealing "genuine" three-body contributions to the triplet structure. The possible role of the low-k features of c^(3) and the implications of our results for dynamic theories of the glass transition are discussed.