Dressing a Nonpolarizable Force Field for OH in TIP4P/2005 Aqueous Solutions with Corrected Hirshfeld Charges.

We present a rigid model for the OH ion parametrized for binary mixtures with TIP4P/2005-type water molecules. Li, Na and K were selected as counterions, hence mimicking the important and widely used solutions of soluble alkaline hydroxides. The optimized atomic charge distributions were obtained by scaling in a factor of 0.85 those derived from the atomic dipole corrected Hirshfeld approach. The agreement between experimental and Molecular Dynamics simulation results is remarkable for a set of properties, namely, the dependence of the density of the solutions on the hydroxide concentration and on temperature, the structure (i.e., positions of the atom-to-atom radial distribution functions and coordination numbers), the viscosity coefficients, the surface tension, or the freezing point depression. The proposed optimized potential parameters for OH thus enlarge the set of models comprised within the Madrid-2019 force field and widen the potential applicability of the TIP4P/2005 water model in basic environments.