(715a) Phase Transition of Water in Graphite and Mica Pores

Recent efforts from molecular simulation of simple and complex systems^1-4 under confinement illustrate non-linear crossover behaviors of critical points from 3D to 2D like with the reduction of pore size. Most of the studies done until now have used simple structureless models for surfaces. In addition, phase diagram calculations are mainly being done using the overall density in the pore as the order parameter. However, it is well known that a fluid phase under confinement is usually inhomogeneous. Hence, the question arises of how different layers under confinement contribute to the overall phase diagram? In the current work, we present the vapor-liquid phase transition, using all atom molecular dynamics simulations, of water confined in graphite and mica slit pores of variable pore sizes ranging from 6 ? 80 Å. We present, in detail, the phase diagrams of the first layer, second layer and middle layer in pores of various sizes and associated critical properties. We also analyze the interfacial thickness of two phase system of different layers. Non-linear cross-over behavior of critical points from 3D to 2D from all-atom simulations is compared with that from previous works.

References:

1. S. Jana, J. K. Singh, and S. K. Kwak, J. Chem. Phys. 130, 214707 (2009). 2. S. K. Singh, A. Sinha, G. Deo, and J. K. Singh, J. Phys. Chem. C 113, 7170 (2009). 3. Y. Lui, A. Z. Panagiotopoulous, and P. G. Debenedetti, J. Chem. Phys. 132 (2010). 4. S. K. Singh, A. Saha, and J. K. Singh, J. Phys. Chem. B 114, 4283 (2010).