Thermodynamics of supercooled water in solutions

Abstract

Molecular dynamics simulations are performed on bulk TIP4P water and on a low concentration aqueous sodium chloride solution. The thermodynamic properties of the systems are studied by analysing the isotherms and the isochores planes. The comparison of the thermodynamics planes of the two systems reveals that modifications beyond a trivial shift occur in the solution. Moreover the limit of mechanical stability and the temperatures of maximum density line can be calculated from the analysis of the thermodynamic planes. While the limit of mechanical stability results unaffected by the presence of the ions, the temperatures of maximum density line is both mildly shifted in temperature and modified in shape in the solution, with respect to bulk water. Signatures of the presence of liquid-liquid coexistence are found in the aqueous solution. The results are also compared to water in a hydrophobic environment and to water confined between hydrophobic plates.