The first water-based solute-solvent system was chosen to be a single Ag + in water, but could have been any single-atom ion. The Ag + -Water cells were created with AmberTools22 , placing a single ion in 17535 water molecules, using the non-bonded Ag + parameters optimized for TIP4P EW from Li & Merz . Since the solvent-cell routine in AmberTools creates water with a very low density, the system was equilibrated for 2 ns in the NPT ensemble at 1 bar, maintained by a Monte Carlo barostat, and then propagated in 2 fs timesteps at 300 K by the Langevin integrator. The final cell dimensions for the production runs were 85.8 Å x 85.8 Å x 85.8 Å . The RDFs were sampled using VMD with a numerical dr of 0.05 Å.