A comparison of force fields for ethanol–water mixtures

Abstract

Aqueous ethanol mixtures are studied through molecular dynamics simulations with the focus on exploring how various force field models reproduce the association and its influence on selected thermo-physical properties of these mixtures. The most important conclusion seems to be the inadequacy of all classical force fields to reproduce the very peculiar shape of the excess enthalpy of these mixtures, as a function of the ethanol concentration, neither quantitatively nor qualitatively. The Kirkwood–Buff (KB) integrals calculated using the simulation data follow the same trends as the experimental ones. This suggests complicated correlation of the excess enthalpy with the concentration fluctuation and clustering in these mixtures. The KB force field shows better overall agreement with experimental results than the other studied models.

Keywords::

• ethanol–water mixture
• force field
• Kirkwood–Buff integral
• micro-heterogeneity

Acknowledgements

We would like to thank the Ministry of Science, Education and Sports of the Republic of Croatia for financially supporting this research. This project was supported by the foundation for Polish science MPD program co-financed by the EU Regional Development fund. Computational part of this work was done using the computer clusters at the University Computing Center (SRCE) in Zagreb, Hybrid Computer Cluster of Department of Physics, University of Split and the Computing Center of Department of Chemistry, Warsaw University.