Relation Between the Widom line and the Strong-Fragile Dynamic Crossover in Systems with a Liquid-Liquid Phase Transition

TL;DR

This study explores the relationship between thermodynamic anomalies and dynamic crossovers near the liquid-liquid critical point in water models and a spherically symmetric potential, suggesting a universal connection across different liquids.

Contribution

It demonstrates a correlation between the Widom line and dynamic fragility transition in models with a liquid-liquid critical point, extending the concept beyond water to other systems.

Findings

Correlation between $C_P^{ m max}$ and dynamic crossover

Evidence of Widom line influence on dynamics in water models

Generalization of the Widom line's role in different liquid systems

Abstract

We investigate, for two water models displaying a liquid-liquid critical point, the relation between changes in dynamic and thermodynamic anomalies arising from the presence of the liquid-liquid critical point. We find a correlation between the dynamic fragility transition and the locus of specific heat maxima $C_P^{\rm max}$ (``Widom line'') emanating from the critical point. Our findings are consistent with a possible relation between the previously hypothesized liquid-liquid phase transition and the transition in the dynamics recently observed in neutron scattering experiments on confined water. More generally, we argue that this connection between $C_P^{\rm max}$ and dynamic crossover is not limited to the case of water, a hydrogen bond network forming liquid, but is a more general feature of crossing the Widom line. Specifically, we also study the Jagla potential, a spherically-symmetric two-scale potential known to possess a liquid-liquid critical point, in which the competition between two liquid structures is generated by repulsive and attractive ramp interactions.