A route to explain water anomalies from results on an aqueous solution of salt

TL;DR

This study uses molecular dynamics simulations to locate the liquid-liquid critical point of water in salt solutions, showing it shifts with salt concentration and suggesting experimental detection is feasible.

Contribution

First simulation-based identification of the water critical point in salt solutions, revealing its shifted position and providing phase diagrams for experimental validation.

Findings

Critical point shifts to higher temperature and lower pressure in salt solutions

Phase diagrams align with experimental data

Detection of the critical point in solutions appears feasible

Abstract

In this paper we investigate the possibility to detect the hypothesized liquid-liquid critical point of water in supercooled aqueous solutions of salts. Molecular dynamics computer simulations are conducted on bulk TIP4P water and on an aqueous solution of sodium chloride in TIP4P water, with concentration c = 0.67 mol/kg. The liquid-liquid critical point is found both in the bulk and in the solution. Its position in the thermodynamic plane shifts to higher temperature and lower pressure for the solution. Comparison with available experimental data allowed us to produce the phase diagrams of both bulk water and the aqueous solution as measurable in experiments. Given the position of the liquid-liquid critical point in the solution as obtained from our simulations, the experimental determination of the hypothesized liquid-liquid critical point of water in aqueous solutions of salts appears possible.