Molecular Insight into the Slipperiness of Ice

Publication date
DOI http://dx.doi.org/10.1021/acs.jpclett.8b01188
Reference B. Weber, Y. Nagata, S. Ketzetzi, F. Tang, W.J. Smit, Bakker, E.H.G. Backus, D. Bonn and M. Bonn, Molecular Insight into the Slipperiness of Ice, J. Phys. Chem. Lett. 9, 11: 2838-2842 (2018)
Group Contact Dynamics

Measurements of the friction coefficient of steel-on-ice over a large temperature range reveal very high friction at low temperatures (−100 °C) and a steep decrease in the friction coefficient with increasing temperature. Very low friction is only found over the limited temperature range typical for ice skating. The strong decrease in the friction coefficient with increasing temperature exhibits Arrhenius behavior with an activation energy of Ea ≈ 11.5 kJ mol–1. Remarkably, molecular dynamics simulations of the ice–air interface reveal a very similar activation energy for the mobility of surface molecules. Weakly hydrogen-bonded surface molecules diffuse over the surface in a rolling motion, their number and mobility increasing with increasing temperature. This correlation between macroscopic friction and microscopic molecular mobility indicates that slippery ice arises from the high mobility of its surface molecules, making the ice surface smooth and the shearing of the weakly bonded surface molecules easy.