Ion hydration in high-density water

Structural modifications of the Zn2+ hydration properties under high pressure (up to 2.85 GPa) have been investigated by Molecular Dynamics (MD) simulations and the first shell structural results have been experimentally validated by X-ray Absorption spectroscopy. The first shell hydration complex of the Zn2+ ion retains an octahedral symmetry with a shortening of the Zn-O distance up to 0.04 angstrom and an increase of the thermal motion. The structural transformations occurring to water with increasing density are also investigated by MD simulations; the effect of pressure is to increase the number of interstitial water molecules, while the tetrahedral first shell cluster is only slightly distorted in the high-density conditions.