Activity Coefficients of Complex Molecules by Molecular Simulation and Gibbs-Duhem Integration

Abstract

Activity coefficients of solvents and solutes in different aqueous solutions of alcohols and polymers are determined by molecular dynamic simulations. These data are often not accessible by simulation due to unacceptably high computational demands. Therefore, we applied a combination of two methods: water activity coefficients were determined directly via Overlapping Distribution Method, while counter-component activity coefficients were calculated indirectly by Gibbs-Duhem integration of the respective water activities. Results are in good agreement with experimental data. The method can easily be applied to determine activity coefficients of very complex components in water or other simple solvents.

Keywords:

• Activity coefficients
• Computer simulation
• Gibbs-Duhem integration
• Molecular dynamics
• Overlapping distributions method
• Polyoxyethylene

ACKNOWLEDGMENT

The authors acknowledge the support from the Deutsche Forschungsgemeinschaft (SPP 1155) by grant SA 700/15. Parts of the calculations were performed on the LiDO compute cluster at Technische Universität Dortmund.

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