Thermodynamics, structure, and dynamics of water confined between hydrophobic plates

Abstract

We perform molecular dynamics simulations of 512 waterlike molecules that interact via the TIP5P potential and are confined between two smooth hydrophobic plates that are separated by 1.10 nm. We find that the anomalous thermodynamic properties of water are shifted to lower temperatures relative to the bulk by Ϸ40 K. The dynamics and structure of the confined water resemble bulk water at higher temperatures, consistent with the shift of thermodynamic anomalies to lower temperature. Because of this T shift, our confined water simulations ͑down to T = 220 K͒ do not reach sufficiently low temperature to observe a liquid-liquid phase transition found for bulk water at T Ϸ 215 K using the TIP5P potential, but we see inflections in P-isotherms at lower temperatures presumably due to the presence of a liquid-liquid critical point. We find that the different crystalline structures that can form for two different separations of the plates, 0.7 and 1.10 nm, have no counterparts in the bulk system, and we discuss the relevance to experiments on confined water.

The puzzling unsolved mysteries of liquid water: Some recent progress

“…In the case of water, a significant change in dynamical properties has been suggested to take place in deeply supercooled states [16,[22][23][24][25]. Unlike other network forming materials [26], water behaves as a non-Arrhenius liquid in the experimentally accessible window [16,27,28].…”

Multilayer Two-Dimensional Water Structure Confined in MoS2

“…[1][2][3][4][5][6][7][8][9][10][11] Inside a one-dimensional channel of carbon nanotubes, for example, water molecules could undergo unconventional phase transitions [12][13] and form ice-like structures at room temperatures depending on the channel diameter. Also, a delicate balance between entropy and enthalpy can render these confined water thermodynamically more stable than the bulk water.…”

Anomalies in a waterlike model confined between plates

“…In order to understand the behavior of water under these limitations a number of experiments and simulations of confined water have been performed. Several types of confinement have been explored: experiments in cylindrical porous [11][12][13] and simulations in carbon nanotubes 14,15 , simulations in porous matrices [16][17][18][19] , experiments 20,21 and simulations in rough surfaces [22][23][24][25][26] and simulations in flat plates 23,25,27,28 .…”

“…Moreover, the presence of layers is also only obtained from indirect evidences. In order to circumvent the difficulties of obtaining the structure of water inside the confined system from experiments, a number of simulations have been performed 23,35,36 .…”