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.