Uniaxial-deformation behavior of ice Ih as described by the TIP4P/Ice and mW water models

Abstract

Using molecular dynamics simulations, we assess the uniaxial deformation response of ice I h as described by two popular water models, namely, the all-atom TIP4P/Ice potential and the coarsegrained mW model. In particular, we investigate the response to both tensile and compressive uniaxial deformations along the [0001] and [0110] crystallographic directions for a series of different temperatures. We classify the respective failure mechanisms and assess their sensitivity to strain rate and cell size. While the TIP4P/Ice model fails by either brittle cleavage under tension at low temperatures or large-scale amorphization/melting, the mW potential behaves in a much more ductile manner, displaying numerous cases in which stress relief involves the nucleation and subsequent activity of lattice dislocations. Indeed, the fact that mW behaves in such a malleable manner even at strain rates that are substantially higher than those applied in typical experiments indicates that the mW description of ice I h is excessively ductile. One possible contribution to this enhanced malleability is the absence of explicit protons in the mW model, disregarding the fundamental asymmetry of the hydrogen bond that plays an important role in the nucleation and motion of lattice dislocations in ice I h .

Atomistic Simulation of Nanoindentation of Ice Ih

“…As such, the formation of effective HBs in this model is not hampered by steric effects, and recrystallization in the presence of a crystalline substrate is facilitated compared to the explicit-proton TIP4P/Ice model. In fact, whether or not HBs are treated explicitly has been shown to fundamentally affect mechanical behavior of ice I h . , …”

“…The cells used for the TIP4P/Ice model correspond to defect-free, proton-disordered ice I h structures with zero total dipole moment . The cells for the mW model correspond to the same structures generated for the TIP4P/Ice model but with the protons removed.…”

“…In this scenario, atomistic simulation techniques can often offer complementary insight, providing a tool for in situ computational "microscopy", 18 capable of providing details of material behavior on atomistic time and length scales. 19,20 This approach has been particularly useful in the interpretation of nanoindentation experiments for providing atomic-scale details of the processes that occur underneath an indenter tip and are inaccessible experimentally. 21−26 Nanoindentation simulations for ice, however, have been extremely scarce.…”

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

“…To describe the interactions between the water molecules, we employ the rigid-molecule TIP4P/Ice model, which is among the best explicit-proton models for water. , It has a melting temperature of T m = 271 K that is close to the experimental value and it has reproduced the presence of a QLL on free surfaces of ice. , The motivation for using an explicit-proton water model instead of the computationally cheaper coarse-grained descriptions in which hydrogen bonding is handled implicitly ,, is that the latter type has been shown to exhibit an excessively ductile kinetics for mechanical deformation processes for ice I h . , …”

“…49,50 The motivation for using an explicit-proton water model instead of the computationally cheaper coarse-grained descriptions in which hydrogen bonding is handled implicitly 39,51,52 is that the latter type has been shown to exhibit an excessively ductile kinetics for mechanical deformation processes for ice I h . 50,53 Equilibration. Prior to the sliding simulations, the GB cells are first equilibrated.…”