(244c) Studies of a Lattice Model of Water Confined in a Slit Pore

There has been much recent interest in the properties of water in confined geometries since this has important applications in understanding water adsorption in carbon materials and in nanotechnology applications of confined water. A key issue in this context is the effect of confinement on the stability of hydrogen bond networks. Recent studies using molecular simulation have addressed this question in relation to the capillary condensation of water in model carbon pores [1]. The results indicate that in general capillary condensation occurs above the bulk vapor pressure indicative of the essential hydrophobicity of a pore in the absence of active sites that might nucleate a hydrogen bond network.

In this paper we describe a study of a lattice model of confined water. The lattice model used is that suggested by Bell and Salt [2] for studying the bulk properties of water and treats the effects of hydrogen bonding through directional nearest neighbor interactions and second neighbor repulsions for molecules on a BCC lattice. We have carried out Monte Carlo simulations of the Bell-Salt model to determine the bulk phase diagram and also the properties of the model when confined in a slit pore geometry. The model gives results that are qualitatively in agreement with our earlier results for the SPC model of water in a slit pore. Since the lattice model is so much simpler than the off-lattice model it should be useful as a tool for studying the effects of confinement on hydrogen bonding and for studies of nanoscale wetting properties of water on solid surfaces.

[1] J. Liu and P. A. Monson, Langmuir, 21, 10219-10225 (2005) [2] G. M. Bell and D. W. Salt, J. Chem. Soc., Faraday Trans. II, 72, 76 (1976)