The temperature and depth dependence of the shear viscosity (η) of the quasi-liquid layer (QLL) of water on ice-I crystals was determined using simulations of the TIP4P/Ice model. The crystals display either the basal {0001} or prismatic {101̅0} facets, and we find that the QLL viscosity depends on the presented facet, the distance from the solid/liquid interface, and the undercooling temperature. Structural order parameters provide two distinct estimates of the QLL widths, which are found to range from 6.0 to 7.8 Å, and depend on the facet and undercooling temperature. Above 260 K, the viscosity of the vapor-adjacent water layer is significantly less viscous than the solid-adjacent layer and is also lower than the viscosity of liquid water.

Nonequilibrium molecular dynamics simulations of solid/liquid friction at ice/water interfaces suggest that the surface density of solid to liquid hydrogen bonds directly correlates with interfacial friction. The basal {0001}, prismatic {101̅ 0}, pyramidal {202̅ 1}, and secondary prism {112̅ 0} facets of ice-I h were drawn through liquid water with a momentum flux between the solid and liquid phases. Solid to liquid hydrogen bonds were identified using local tetrahedral ordering of the water molecules. An expression for friction coefficients appropriate for negative slip boundary conditions is presented, and the computed friction of these interfaces is found to be invariant to the shear rate and direction of shear relative to the surface features. Structural and dynamic interfacial widths for all four facets were found to be similar (6.6−9.5 Å structural and 9−15 Å dynamic) and are largely independent of the shear rate and direction. Differences in the solid to liquid hydrogen bond density are explained in terms of surface features of the four facets. Lastly, we present a simple momentum transmission model using the density of solid/liquid hydrogen bonds, the shear viscosity of the liquid, and the structural width of the interface.

We have investigated the structural and dynamic properties of the basal and prismatic facets of the ice Ih/water interface when the solid phase is drawn through the liquid (i.e., sheared relative to the fluid phase). To impose the shear, we utilized a velocity-shearing and scaling approach to reverse non-equilibrium molecular dynamics. This method can create simultaneous temperature and velocity gradients and allow the measurement of transport properties at interfaces. The interfacial width was found to be independent of the relative velocity of the ice and liquid layers over a wide range of shear rates. Decays of molecular orientational time correlation functions gave similar estimates for the width of the interfaces, although the short- and longer-time decay components behave differently closer to the interface. Although both facets of ice are in "stick" boundary conditions in liquid water, the solid-liquid friction coefficients were found to be significantly different for the basal and prismatic facets of ice.

No abstract

We present evidence that the prismatic and secondary prism facets of ice-I h crystals possess structural features that can reduce the effective hydrophilicity of the ice/water interface. The spreading dynamics of liquid water droplets on ice facets exhibits long-time behavior that differs for the prismatic {10 10} and secondary prism {11 20} facets when compared with the basal {0001} and pyramidal {20 21} facets. We also present the results of simulations of solid-liquid friction of the same four crystal facets being drawn through liquid water, and find that the two prismatic facets exhibit roughly half the solid-liquid friction of the basal and pyramidal facets. These simulations provide evidence that the two prismatic faces have a significantly smaller effective surface area in contact with the liquid water. The ice / water interfacial widths for all four crystal facets are similar (using both structural and dynamic measures), and were found to be independent of the shear rate. Additionally, decomposition of orientational time correlation functions show position-dependence for the short-and longer-time decay components close to the interface.