Phase Transitions of Water in Graphite and Mica Pores

We report all-atom molecular dynamics simulations of water confined in graphite and mica slit pores of variable size ranging from 10 to 60 A°. For each pore size, we demonstrate that the confinement not only reduces the critical temperature of the water but also introduces inhomogeneity in the system that, in turn, results in different vapor-liquid coexistence densities at different layers of the pore. We report, in detail, the contribution of different layers toward the vapor-liquid phase diagram of the confined water in graphite and mica slit pores. We also present the hydrogen bonding (HB) distribution in various layers and the ordering of water molecules near the surface of pore. Bond orientational order calculations of water near the surface of the pores indicate that water molecules tend to order near the mica surface whereas the ordering is absent for the case of graphite pores.