Structure of water adsorbed on a mica surface.

Monte Carlo simulations of hydration water on the mica (001) surface under ambient conditions revealed water molecules bound closely to the ditrigonal cavities in the surface, with a lateral distribution of approximately one per cavity, and water molecules (interposed between K+ counter ions) in a layer situated about 2.5 A from a surface O along a direction normal to the (001) plane. The calculated water O density profile was in quantitative agreement with recent x-ray reflectivity measurements indicating strong lateral ordering of the hydration water but liquidlike disorder otherwise.