The Importance of Polarizability in the Modeling of Solubility: Quantifying the Effect of Charged Co-Solutes On the Solubility of Small Non-Polar Solutes

In recent work,¹ we demonstrated that the addition of polarizability to a simple Lennard-Jones (LJ) model for various small non-polar solute molecules results in quantitative agreement with experiment for the solubility of these molecules in the recent reparameterization of the TIP4P water model (i.e. TIP4P/2005 and TIP4P-Ew). In this work we consider the effect of charged co-solvents (i.e. salting-out). We will begin by showing that, contrary to current opinion,^2,3 the use of a polarizable solute, together with the TIP4P/2005 and TIP4P-Ew water models, is insufficient to correctly describe the salting-out of small non-polar solutes (Ne, Ar, Kr, Xe and methane) from aqueous solution. We will follow this by demonstrating that these models fail due to an inaccurate solute-water interaction potential.

¹       P.J. Dyer, H. Docherty and P.T. Cummings, J. Chem. Phys. 129, 02450 (2008)

²       H. Docherty, A. Galindo, E.Sanz and C. Vega, J. Phys. Chem. B. 111, 8993 (2007)

³       J. Holzmann, R. Ludwig, A. Geiger and D. Paschek, ChemPhysChem 9, 2722 (2008)