Water in Nanopores: III. Surface Phase Transitions of Water on Hydrophilic Surfaces

Abstract

Water in hydrophilic pores shows a rich phase diagram due to the appearance of the surface phase transitions. By simulation studies of water in various hydrophilic pores, we have analyzed the evolution of the water phase diagram with the strengthening of a water−wall interaction potential U0. A second-order wetting transition is observed rather close to the liquid−vapor critical temperature when U0 ≈ −2 kcal/mol. The wetting temperature rapidly decreases with the strengthening of a water−wall interaction. A first-order wetting transition, accompanied by a prewetting transition, is observed when the hydrophilicity of the walls is within the range of −4 ≤ U0 ≤ −3 kcal/mol. At U0 ≤ −4 kcal/mol, the temperature of the wetting transition is below the bulk freezing temperature, and one or two layering transitions appear instead of the prewetting transition. Coexistence curves of the first layering transition are well described by the two-dimensional Ising model with critical exponent β = 0.125. The critical tem...