Super-Arrhenius temperature dependent viscosity due to liquid-liquid phase separation in the super-cooled Kob-Andersen model

TL;DR

This paper investigates the liquid-liquid phase separation in the supercooled Kob-Andersen model, linking it to super-Arrhenius viscosity behavior and glass transition mechanisms through a novel order parameter and Markov Network modeling.

Contribution

It introduces the use of the weighted coordination number to analyze phase separation and extends the approach to model viscosity changes near the glass transition.

Findings

Liquid-liquid phase separation is observed in the supercooled Kob-Andersen system.

The study verifies local equilibrium of phase separation using density and pressure profiles.

A Markov Network Model estimates temperature-dependent viscosity from interfacial information.

Abstract

In this study, a recently introduced order parameter called the weighted coordination number (WCN) was used to investigate the liquid-liquid (LL) phase separation, indicating temperature-dependent coarsening of the LL interface as a possible mechanism for the glass transition. A well-established glass-forming Kob-Andersen binary Lennard-Jones system was used in this study. The gas-liquid binodal line was reconstructed using WCNs, and the same approach was extended to study the liquid-liquid binodal line. Systems of various densities are instantaneously quenched from high to low temperatures where liquid-liquid separation is observed. The densities and composition of each liquid state were used to verify the level rule, along with the density and pressure profiles, demonstrating the local equilibrium of liquid-liquid phase separation. The transition from the liquid-liquid phase separation in the supercooled region to the glass transition region was modeled by adopting a Markov Network Model to estimate the temperature-dependent viscosity using liquid-liquid interfacial information from the classification.