Water in nanopores: II. The liquid–vapour phase transition near hydrophobic surfaces

Abstract

The liquid-vapour phase transition near a weakly attractive surface is\nstudied by simulations of the coexistence curves of water in hydrophobic pores.\nThere is a pronounced gradual density depletion of the liquid phase near the\nsurface without any trend to the formation of a vapour layer below the bulk\ncritical temperature Tc. The temperature dependence of the order parameter in\nthe surface layer follows the power law (rol - rov) ~ (1 - T/Tc)^beta1 with a\nvalue of the exponent beta1 close to the critical exponent beta1 = 0.82 of the\nordinary transition in the Ising model. The order parameter profiles in the\nsubcritical region are consistent with the behaviour of an ordinary transition\nand their temperature evolution is governed by the bulk correlation length.\nDensity profiles of water at supercritical temperatures are consistent with the\nbehaviour of the normal transition caused by the preferential adsorption of\nvoids. The relation between normal and ordinary transitions in the Ising model\nand in fluids is discussed.\n