title: Optimization of classical nonpolarizable force fields for OH(-) and H3O(+).
abstract: We optimize force fields for H3O(+) and OH(-) that reproduce the experimental solvation free energies and the activities of H3O(+) Cl(-) and Na(+) OH(-) solutions up to concentrations of 1.5 mol/l. The force fields are optimized with respect to the partial charge on the hydrogen atoms and the Lennard-Jones parameters of the oxygen atoms. Remarkably, the partial charge on the hydrogen atom of the optimized H3O(+) force field is 0.8 ± 0.1|e|--significantly higher than the value typically used for nonpolarizable water models and H3O(+) force fields. In contrast, the optimal partial charge on the hydrogen atom of OH(-) turns out to be zero. Standard combination rules can be used for H3O(+) Cl(-) solutions, while for Na(+) OH(-) solutions, we need to significantly increase the effective anion-cation Lennard-Jones radius. While highlighting the importance of intramolecular electrostatics, our results show that it is possible to generate thermodynamically consistent force fields without using atomic polarizability.
authors.affiliation: Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Oxford OX1 3NP, United Kingdom.
authors.forename: Douwe Jan
authors.initials: DJ
authors.lastname: Bonthuis
authors.affiliation: Ion-Plasma and Laser Technologies Institute of the Uzbekistan AS, Tashkent, Uzbekistan.
authors.forename: Shavkat I
authors.initials: SI
authors.lastname: Mamatkulov
authors.affiliation: Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany.
authors.forename: Roland R
authors.initials: RR
authors.lastname: Netz