MD simulation of water at imperfect platinum surfaces .2. electrostatics

Three-dimensional electrostatic potential distributions of a series of platinum\water interfaces were calculated from trajectories of molecular dynamics simulations. The electrostatic potential within the adsorbed layer shows periodic features reflecting the structure of water. It is negative at a point vacancy, due to the water molecule that occupies it. In Vacant adsorption sites the potential is close to zero, thus ion adsorption can take place there. The potential around platinum atoms at the step edge varies spatially between highly negative and positive values, therefore ion adsorption may not be possible there. However, the potential is generally close to zero near platinum atoms under the step edge, thus these atoms are open for adsorption. The corner platinum atoms of a monoatomic rectangular terrace are surrounded with highly negative and positive potentials along the steps, but they can be reached from the (011) direction because the potential is only slightly positive there. In a kink site the electrostatic potential is close to zero and the kinks are usually open towards the bulk, thus they can serve as starting points for adsorption processes or electrochemical reactions. (C) 1997 Elsevier Science S.A.