Atomistic Simulation of Nanoindentation of Ice Ih

Abstract

Using molecular dynamics simulations, we study the nanoindentation response of the ice Ih basal surface using two popular water models, namely, the all-atom TIP4P/Ice potential and the coarse-grained mW model. In particular, we consider two markedly different temperatures at which a quasi-liquid layer (QLL) is or is not present. We discuss loading curves, hardness estimates, deformation mechanisms, and residual imprints, considering the effect of the QLL, indenter size, and penetration rate. At very low temperatures, in the absence of a QLL, both potentials produce similar loading curves and deformation mechanisms. Close to the melting temperature, however, important differences were found, including deviations in the QLL thickness and fraction as well as the presence of a competition between pressure-induced melting and recrystallization events. Nevertheless, both potentials exhibit similar deformation mechanisms and steady-state hardness estimates that are consistent with experimental data. In addition to contributing to the discussion regarding the interpretation of experimental AFM loading curves, the present results provide valuable information concerning the simulation of contact problems involving ice and the behavior of these two popular water models under such circumstances.