Solubility of nonpolar solutes in water: Computer simulations using the CF1 central force model

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Abstract
Nonpolar solutes in water are modeled by the CF1 central force model for the water-water interactions and a shifted-force Lennard-Jones potential function for the solute-water interactions. Thermodynamic integration is used to calculate the solvation free energy of solutes of various sizes. A systematic exploration of the effect of the size of the solute and the depth of the potential well is carried out. This allows an examination of the change in the solvation free energy as the solute size and potential well depth are independently varied. The solvation free energies of the noble gas series are also studied. The results compare favorably with experiment and previous studies, indicating the suitability of the CF1 model of water for use in free energy calculations. An information theory approximation is used to calculate the solvation free energy for hard spheres of various sizes from a simulation of pure CF1 water. The results of this approximation show trends similar to the results of our simulations using the modified shifted-force potentials.