Abstract
A statistical mechanical formulation is presented for the entropy of solution of simple molecules in water. The formulation is based on the Green-Wallace expansion for the entropy in terms of multiparticle correlation functions, which is derived here for rigid polyatomic fluids and for mixtures. With a factorization assumption for the solute-water correlation function we have been able to separate the translational and orientational contributions to the entropy of solution. This approach is applied to an infinitely dilute solution of methane in water. The required correlation functions are obtained by Monte Carlo simulation. The orientational contribution, which is due directly to the orientational asymmetry of water-water interactions, is found to be comparable to the translational contribution. We find that the large entropies and heat capacities of hydrophobic hydration can be accounted for by solute-water correlations alone and that large perturbations in water structure are not required to explain hydrophobic behavior.
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Acknowledgements
We are grateful to Prof. R.H. Wood for numerous helpful discussions. We also thank Prof. W.L. Jorgensen for making the program BOSS available to us and Dr. Wallace for communicating to us unpublished results. This work was supported by the National Science Foundation (grant CPE8351228). Partial support was also provided by Union Carbide, Merck and Exxon.
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Lazaridis, T., Paulaitis, M.E. Entropy of Hydrophobic Hydration: A New Statistical Mechanical Formulation. MRS Online Proceedings Library 278, 319–324 (1992). https://doi.org/10.1557/PROC-278-319
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DOI: https://doi.org/10.1557/PROC-278-319