Extrapolating Single Organic Ion Solvation Thermochemistry from Simulated Water Nanodroplets

International audienceWe compute the ion/water interaction energies of methylated ammonium cations and alkylated carboxylate anions solvated in a large nanodroplet of 10,000 water molecules from 10 ns molecular dynamics simulations and from an all-atom polarizable force-field approach. Together with our earlier results concerning the solvation of these organic ions in nanodroplets whose molecular sizes range from 50 to 1,000, these new data allow us to discuss the reliability of extrapolating absolute single-ion bulk solvation energies from small ion/water droplets using common power-law functions of the cluster size. We show that reliable estimates of these energies can be extrapolated from a small data set comprising the results of three droplets whose sizes are included between 100 and 1,000 using a basic power law function of the droplet size. This agrees with the earlier conclusion drawn from a model built within the mean-spherical framework and paves the road towards a theoretical protocol to systematically compute the solvation energies of complex organic ions