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

Wed, 31 Dec 2008 23:00:00 GMT

Effect of concentration on the thermodynamics of sodium chloride aqueous solutions in the supercooled regime Corradini, Dario; Gallo, Paola; Rovere, Mauro 2009 The journal of chemical physics 130 154511 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.

Mode-coupling behavior of a Lennard-Jones binary mixture upon increasing confinement

Wed, 31 Dec 2008 23:00:00 GMT

Mode-coupling behavior of a Lennard-Jones binary mixture upon increasing confinement Gallo, Paola; Attili, Andrea; Rovere, Mauro 2009 Physical Review E 80 061502 Molecular dynamics simulations are performed on a Lennard Jones binary mixture confined in off lattice matrices of soft spheres with increasing radius. We focus on dynamics upon supercooling and in particular on testing the mode coupling theory properties of the confined mixture. Parameters of mode coupling theory in going from bulk to weak confinement, and from weak to strong confinement are extracted from simulations and analyzed. We focus on the study of the behavior of the single particle density correlators. We find that the mode coupling theory retains its validity also in the case of strong confinement, with a reduction of range of validity. The role of hopping is discussed in relation with the differences between the results obtained from the diffusion coefficients and the mode coupling theory predictions.

Thermodynamics of supercooled water in solutions

Wed, 29 Jul 2009 22:00:00 GMT

Thermodynamics of supercooled water in solutions Corradini, Dario; Gallo, Paola; Rovere, Mauro 2009-07-30 Journal of Physics: Conference Series 177 012003 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 analyzing 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.