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

Dipartimento di Fisica, Università Roma Tre, Via della Vasca Navale 84, I-00146 Roma, Italy.
The Journal of Chemical Physics (Impact Factor: 3.12). 05/2009; 130(15):154511. DOI: 10.1063/1.3119634
Source: PubMed

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 isochores planes 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 water for 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 of a liquid-liquid coexistence are found for both concentrations.

1 Follower
  • [Show abstract] [Hide abstract]
    ABSTRACT: The physical properties of aqueous sodium chloride solutions have been studied theoretically, but so far no experimental data has been obtained under supercooled conditions. Here the results of 1H NMR translational diffusion measurements of water in sodium chloride solutions in the temperature range 230 to 300 K and sodium chloride concentrations up to 4.2 mol/kg are presented. It was found that the diffusion data were well described by the Vogel-Tamman-Fulcher relationship with concentration dependent parameters D 0 , B 0 and T 0 . The results indicate that under supercooled conditions the influence of sodium chloride on water diffusion is much smaller than predicted by molecular dynamic simulations.
    The Journal of Physical Chemistry A 04/2014; 118(18). DOI:10.1021/jp501472s · 2.78 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Molecular dynamics results are presented for bulk TIP4P water and for aqueous solutions of sodium chloride at two different concentrations. Thermodynamical and structural properties are calculated in the supercooled region. The behaviour in the thermodynamic plane is compared with the case of water in interaction with a hydrophobic environment. Structural modifications induced by the hydrophilic and hydrophobic interactions are discussed. It is found that the phase diagram of water is shifted in different directions in the case of the hydrophobic system and the ionic solutions. The region inside the temperatures of the maximum density curve is reduced upon increasing the concentration of ions.
    Journal of Molecular Liquids 02/2011; 159(1):18-23. DOI:10.1016/j.molliq.2010.03.017 · 2.08 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We study the structural properties of aqueous solutions of potassium chloride and fluoride at ambient conditions and upon supercooling with the use of molecular dynamics. We perform the calculations at increasing concentration in a range from 0.67 mol/kg up to 3.96 mol/kg. We investigate the modifications of the hydration shells and the changes in the water structure induced by the presence of the ions. The oxygen–oxygen structure is strongly dependent on the ionic concentration while the hydrogen bonding is well preserved. The results show that increasing the ion concentration is analogous to increase pressure on pure water. The KF salt has a stronger effect on water due to the fluoride anion. F− appears also more effective as substitutional of the oxygen in the water network with possible relevant consequences on the tendency of water to transform to the high density phase.
    Journal of Molecular Liquids 07/2013; 189:52. DOI:10.1016/j.molliq.2013.05.023 · 2.08 Impact Factor


Available from