(387e) Computational Investigation of Glassy Water in Nano-Scale Confinement

We use molecular dynamics simulations to study the structure, thermodynamics, and mechanical properties of glassy water under nanoscale confinement between surfaces with tunable hydrophobicity and hydrophilicity [1]. Surface interactions are modified by scaling the dipole moments of surface charge-groups, giving a homogeneous surface, or by removing charge-groups from the surface, creating a heterogeneous surface with random or ordered hydrophilicty. We study both quenched and mechanically stable configurations (inherent structures) [2] over broad ranges of density and quench rates. The relation between the lateral components of the stress tensor and density, that is to say the equation of state of the energy landscape for this confined system [3], exhibits complex dependence on the surface chemistry and degree of confinement. Under hydrophobic confinement, multiple minima in the landscape equation of state appear which are indicative of a first-order transition between two liquid phases. Isochoric quenches at sufficiently low density result in cohesive or adhesive failure [4], depending on the hydrophobic or hydrophilic nature of the confining surfaces.

[1] T.G. Lombardo, F.H. Stillinger and P.G. Debenedetti, Thermodynamic Mechanism for Solution Phase Chiral Amplification via a Lattice Model. Proc. Nat'l. Acad. Sci. USA, DOI: 10.1073/pnas.0812867106, 2009.

[2] Stillinger, F.H., and Weber, T.A., Phys. Rev. A, 25, 978, 1982.

[3] Debenedetti, P.G., Stillinger, F.H., Truskett, T.M., and Roberts, C.J., J. Phys. Chem. B, 103, 7308, 1999.

[4] Shah, P., and Truskett, T.M., Mechanics of Mater., 38, 924, 2006.