Effect of concentration on the thermodynamics of sodium chloride aqueous solutions in the supercooled regime

TL;DR

This study uses molecular dynamics simulations to explore how sodium chloride concentration affects the thermodynamic behavior of aqueous solutions in the supercooled regime, revealing shifts in density maxima and indications of liquid-liquid coexistence.

Contribution

It provides new insights into the thermodynamic properties and stability limits of supercooled sodium chloride solutions at different concentrations.

Findings

Isotherms and isochores shift to lower pressures with increased concentration.

Temperature of maximum density shifts to lower pressures and temperatures.

Evidence of liquid-liquid coexistence in supercooled solutions.

Abstract

Molecular Dynamics simulations are performed on two sodium chloride solutions in TIP4P water with concentrations c=1.36 mol/kg and c=2.10 mol/kg upon supercooling. The isotherms and isochoresplanes are calculated. The temperature of maximum density line and the limit of mechanical stability line are obtained from the analysis of the thermodynamic planes. The comparison of the results shows that for densities well above the limit of mechanical stability, the isotherms and isochores of the sodium chloride aqueous solution shift to lower pressures upon increasing concentration while the limit of mechanical stability is very similar to that of bulk waterfor both concentrations. We also find that the temperature of maximum density line shifts to lower pressures and temperatures upon increasing concentration. Indications of the presence ofa liquid-liquid coexistence are found for both concentrations.