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Entropy of Hydrophobic Hydration: A New Statistical Mechanical Formulation

Published online by Cambridge University Press:  26 February 2011

Themis Lazaridis
Affiliation:
University of Delaware, Department of Chemical Engineering, Newark, Delaware 19716
Michael E. Paulaitis
Affiliation:
University of Delaware, Department of Chemical Engineering, Newark, Delaware 19716
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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.

Type
Research Article
Copyright
Copyright © Materials Research Society 1992

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