H3O+and OH−in Water

Abstract Using the KKY potential model, we have carried out classical molecular dynamics (MD) simulations of structural and vibrational properties of H3O+ and OH− in water. We have started simulation from an initial configuration that contains both H3O+ and OH− simultaneously in a bulk water. As for H3O+ in water, we have obtained a structure in qualitatively agreement with a structure of (H9O4)+ predicted previously by ab initio calculations. However, the O[sbnd]O distances between H3O+ and its coordinated water molecules were larger than the previous ab initio calculation. As for OH− in water, we have obtained that around OH− ion, the number of solvated water molecules is larger than in the case of pure water. The O[sbnd]H stretching vibration frequency of H3O+ and OH− were shifted to the red and to the blue, respectively, compared to that for H2O, which is in agreement with the result of ab initio MD simulation by Tuckerman et al.