Ab initio molecular dynamics simulation of the OH radical in liquid water

We present the first results of a density functional theory molecular dynamics of the hydroxyl radical using the BLYP exchange-correlation density functional. The simulations predict formation of a well defined and relatively stable first coordination shell of the hydrated OH. The local environment of the radical is characterized with three hydrogen bonded and one hemibonded water molecules. The unpaired electron is in these simulations tied up in the hemibond to the oxygen of a solvent water molecule. This suggests that the widespread picture of rapid diffusion of OH radical in water through H abstraction chain reaction may need to be reconsidered, although the question should be raised to what extent this effect is overestimated by the known tendency of BLYP to overestimate hemibonded structures.