Effect of hydrophobic solutes on the liquid-liquid critical point

TL;DR

This study uses molecular dynamics simulations to explore how hydrophobic solutes affect the liquid-liquid critical point in Jagla ramp particle solutions, revealing shifts in critical parameters and preserved diffusion anomalies.

Contribution

It introduces a detailed simulation analysis of hydrophobic solutes' effects on the liquid-liquid critical point in Jagla ramp particle solutions, highlighting how solute concentration influences phase behavior.

Findings

Liquid-liquid critical point persists up to high solute concentrations.

Critical point shifts to higher pressures and lower temperatures with increased solute.

Diffusion anomalies remain across all studied solute mole fractions.

Abstract

Jagla ramp particles, interacting through a ramp potential with two characteristic length scales, are known to show in their bulk phase thermodynamic and dynamic anomalies, similar to what is found in water. Jagla particles also exhibit a line of phase transitions separating a low density liquid phase and a high density liquid phase, terminating in a liquid-liquid critical point in a region of the phase diagram that can be studied by simulations. Employing molecular dynamics computer simulations, we study the thermodynamics and the dynamics of solutions of hard spheres (HS) in a solvent formed by Jagla ramp particles. We consider the cases of HS mole fraction x = 0.10, 0.15 and 0.20, and also the case x = 0.50 (a 1:1 mixture of HS and Jagla particles). We find a liquid-liquid critical point, up to the highest HS mole fraction; its position shifts to higher pressures and lower temperatures upon increasing x. We also find that the diffusion coefficient anomalies appear to be preserved for all the mole fractions studied.