Effects of Temperature on the Thermodynamic and Dynamical Properties of Glycerol-Water Mixtures: A Computer Simulation Study of Three Different Force Fields

摘要

Glycerol water solutions are relevant in technological and scientific applications, such as in the preservation of biomolecules and tissues at low temperatures. We perform molecular dynamics Simulations of glycerol-water mixtures with glycerol molar fractions of chi(g) = 0-100% at P = 0.1 MPa and T = 210-460 K. We focus On the effects of temperature and concentration on the thermodynamic (density rho, thermal expansion coefficient alpha(p), isobaric specific heat c(p), compressibility K-T) and dynamical (glycerol and water diffusion coefficients, D-g and D-w) properties of the mixtures. In particular, we test the sensitivity of computer simulation results to the glycerol force field and water model (TIP3P and TIP4P/2005) employed. All mixture models underestimate rho at high T and tend to overestimate rho at low T-j only the mixture model based on TIP4P/2005 water exhibits a density maximum at low chi(g), as expected. All models overestimate alpha(p), c(p), and K-T; they are able to reproduce qualitatively the T dependence of alpha(p) and K-T but fail in the case of c(p). In all cases, D-g and D-w follow the Vogel Tamman Fulcher equation and decouple at low T, with D-w/D-g increasing upon cooling. Overall, the mixture based on TIP4P/2005 water provides better thermodynamic and dynamical properties than the mixtures based on TIP3P water, even chi(g) = 20%.