Crossover between Equilibrium and Shear-controlled Dynamics in Sheared Liquids

TL;DR

This study uses simulations to identify a transition line in sheared liquids where dynamics shift from equilibrium-controlled to shear-controlled, revealing how shear rate and temperature influence particle motion.

Contribution

It introduces a detailed numerical analysis of the crossover between equilibrium and shear-controlled regimes in sheared liquids, highlighting the role of a specific transition line.

Findings

A transition line separates equilibrium and shear-controlled regions.

Structural relaxation time is inversely proportional to shear rate along this line.

Above the line, shear flow does not affect the liquid dynamics.

Abstract

We present a numerical simulation study of a simple monatomic Lennard-Jones liquid under shear flow, as a function of both temperature and shear rate. By investigating different observables we find that i) It exists a line in the (temperature-shear) plane that sharply marks the boarder between an ``equilibrium'' and a ``shear-controlled'' region for both the dynamic and the thermodynamic quantities; and ii) Along this line the structural relaxation time, is proportional to the inverse shear rate, i.e. to the typical time-scale introduced by the shear flow. Above the line the liquid dynamics is unaffected by the shear flow, while below it both temperature and shear rate control the particle motion.