Water Density in the Double Layer

A recently proposed approach to the problem of ion hydration in solutions is extended to water at a charged metallic electrode. Water in the closest proximity of the electrode is compressed due to electrostriction and the dipole moments of H 2 O molecules become completely ordered by extremely strong electric field created by the surface charge. It is estimated that for common values of the charge density of the order of 10 -1 C m -2 the effect of striction corresponds to that of pressures of the order of gigapascals. A consistency between the present approach and recent X-ray measurements of the density of water at a silver electrode is discussed.