Phase Diagram of Electrostricted H 2 O at Surfaces of Electrodes at 273–373 K: Electric Critical Point of Water

The equation of state of an open system containing water in an electric field of strength E greater than 10 8 V m −1 leads to a phase diagram with two‐phase and single‐phase regions in the Π,E,T coordinates ( Π =electrostriction pressure). The phases differ by their degree of orientation of H 2 O molecules in the field. The phase transition is discontinuous with respect to E . The calculation shows that the discontinuity vanishes at the critical point: Π c ≈0.2 GPa, E c ≈10 9 V m −1 and ${{\rm T}{{{\rm E}\hfill \atop c\hfill}}}$ below 313 K. The thermal effect of the transition is calculated and compared with an experiment at the Hg/aqueous electrolyte interface found in the literature.