The reorientation mechanism of hydroxide ions in water: A molecular dynamics study

Classical molecular dynamics simulations with a polarizable force field indicate two major structural motifs for the aqueous bulk solvation of OH−: a four- and a five-coordinated solvent hydrogen bond donor to OH− in addition to a weak solvent hydrogen bond acceptor by OH−. A two-step mechanism for the reorientation of OH− in water is proposed: first, the reorientation of OH− is initiated by the coupled translation with the water molecules in its first solvation shell; second, the OH− relaxes to the minimum energy configuration. The first step is the rate-limiting one for this mechanism.