Grain-Boundary Sliding in Ice I_h: Tribology and Rheology at the Nanoscale

Abstract

Using nonequilibrium molecular dynamics simulations, we investigate the process of grain-boundary (GB) sliding in ice I h . We focus on the ∑35 symmetric tilt boundary, which has been observed experimentally in polycrystalline samples, and employ the explicit-proton TIP4P/Ice model to describe the interactions between the water molecules. In all cases, the sliding process closely resembles that observed in viscoelastic substances. After an initial linear elastic regime, the stress−strain response passes through a yield-stress maximum that triggers the onset of rheological response through grain sliding, followed by a final relaxation toward a stationary sliding regime. To assess the role of the molecular structure and dynamics of the GB region, we impose various sliding velocities and directions, as well as appraise different temperatures. In particular, we contrast two cases: one in which the GB interface features the presence of a liquid-like layer at 250 K and another in which there is not, at 150 K. In all cases, we find that the liquid-like layer significantly facilitates GB sliding, acting as a boundary lubricant. Both the yield stress as well as the steady-state stress required to maintain sliding, which can be interpreted in terms of effective static and dynamic frictional forces, respectively, are significantly lower than those obtained at 150 K. Whereas in the latter case, the GB region undergoes large-scale amorphization in the frictional process; the thickness of the liquid-like layer at 250 K only increases moderately, reflecting its effectiveness in facilitating the sliding process. The present results provide valuable information regarding the viscous relaxation processes and the role of the disordered GB layer in the frictional behavior at the nanoscale during GB sliding in ice I h .

Ice friction at the nanoscale

“…To prevent strain effects in the parallel direction, the lattice parameters are set to the equilibrium value at pressure p z . Shear was imposed on ice by moving the walls tangentially in the x direction at a constant sliding speed (with opposite direction on each wall) ( 2 , 32 , 38 , 48 ). All Lennard-Jones interactions were truncated beyond 1 nm.…”

“…Experimental confirmation of interfacial premelting films in the order of the nanometer does not resolve the controversy ( 16 – 21 ), as it is arguable whether macroscopic hydrodynamics assumed in most theories ( 22 – 24 ) is obeyed at such small length scales ( 25 ). In fact, computer simulations of flow under confinement reveal consistent violation of the stick boundary condition and the significance of water slip ( 26 – 30 ), while studies of water sliding on ice and grain boundary friction suggest negative slip instead ( 31 , 32 ).…”

Patterning Configuration of Surface Hydrophilicity by Graphene Nanosheet towards the Inhibition of Ice Nucleation and Growth

“…Figure 6a suggests that a stunting effect exists during the growth process of an ice crystal on a metal-graphene nanosheet surface. This is due to the boundary misorientation between ice crystals [47], as illustrated in Figure 6b. Obviously, the ice cluster marked with a red circle has a different orientation with the ice cluster on the right side.…”

“…A different surface configuration resulted in varying levels of ice growth inhibition. We also discussed the misorientation between grain boundaries of the ice crystal [47].…”