Strong layering effects and anomalous dynamical behaviour in confined water at low hydration.

Molecular dynamics results on water con fined in a silica pore in the lowhydration regime are presented. Strong layering effects are found due to the hydrophilic character of the substrate. The local properties of water are studied as a function of both temperature and hydration level. The interaction of the thin films of water with the silica atoms induces a strong distortion of the hydrogen bond network. The residence time of the water molecules is dependent on the distance from the surface. Its behaviour shows a transition from a Brownian to a non-Brownian regime on approaching the substrate in agreement with results found in studies of water in contact with globular proteins. The confined liquid at low hydration shows upon supercooling an anomalous behaviour which is rather different to that in the high-hydration regimes already studied.