A charged ring model for classical OH−(aq) simulations

We propose a new ‘charged ring’ (CR) model to better represent the delocalized electron density of the oxygen atom of hydrated OH− in classical molecular simulations. This approach corrects a major defect of traditional point-charge models, which inaccurately predict that OH− accepts predominantly 5–6 hydrogen bonds in aqueous solution. Classical molecular dynamics simulations with the CR model of OH− result in ∼4 accepted H-bonds, in agreement with recent neutron diffraction data and ab initio molecular dynamics results. The observed competition between 3- and 4-coordinate OH−(aq) structures is also in good agreement with ab initio results.