PNNL

Abstract

simulations with polarizable potential models. Two major solvation structures of OH- were suggested by our study. One of which has four accepted hydrogen bonds from water and the other has five accepted hydrogen bonds. A weak hydrogen bond donated by the hydroxide ion was observed in our simulations. The simulated reorientation relaxation times of OH- are in qualitative agreement with CTTS experiments. We propose a two-step mechanism for the reorientation of hydroxide ions in water. First, the reorientation of OH- is initiated by the coupled translation with water molecules in its first solvation shell. Second, the OH- hydrogen relaxes to the minimum energy state. The rate-limiting step in this mechanism is the first step, translation diffusion of the first solvation shell water molecules. The activation energies of reorientation of OH- and translation of H2O determined from our simulations are 22.5 and 18.5 kJ/mol, respectively. These values fall in the range of the measured data. This work was supported by the US Department of energy's Office of Basic Energy Sciences, Chemical Sciences program. Pacific Northwest national Laboratory is operated by Battelle for the US Department of Energy.