Solute-induced water structure: computer simulation on a model system.

Two series of Monte Carlo simulations have been carried out on a system consisting of 125 water molecules, one of which is kept fixed to simulate a water molecule whose mobility is restricted by a solute. The results are checked against similar simulations without restrictions, used as a control, and they show how the blocked molecule helps increase both the structural order and the connectivity of the hydrogen bond network. Cooperativity originating from proton polarizability of H-bonds and/or from many-body terms of interaction potentials cannot be involved since we use a rigid water model and ab initio pair potentials. The present findings are interpreted as indicative of a motion-dependent effect which is triggered by the blocked molecule and propagates along H-bonds. As has already been proposed, this effect might play a role in water-mediated solute--solute interactions.