Anomalous structural evolution of soft particles: Equibrium liquid state theory

TL;DR

This paper uses liquid state theory to predict an anomalous nonmonotonic evolution of the pair correlation function in soft particles, supported by simulations, revealing a structural anomaly due to particle softness.

Contribution

It introduces a theoretical framework predicting a nonmonotonic structural anomaly in soft particles, supported by simulations, highlighting the role of particle softness in equilibrium structural evolution.

Findings

Prediction of nonmonotonic peak evolution with density

Identification of a temperature-dependent S-shaped evolution

Support from computer simulations confirming theoretical predictions

Abstract

We use the hyper-netted chain approximation of liquid state theory to analyze the evolution with density of the pair correlation function in a model of soft spheres with harmonic repulsion. As observed in recent experiments on jammed soft particles, theory predicts an `anomalous' (nonmonotonic) evolution of the intensity of the first peak when density is increased at constant temperature. This structural anomaly is a direct consequence of particle softness, and can be explained from purely equilibrium considerations, emphasizing the generality of the phenomenon. This anomaly is also predicted to have a non-trivial, `${\cal S}$-shaped', evolution with temperature, as a result of a competition between three distinct effects, which we describe in detail. Computer simulations support our predictions.