Abstract

We apply the capillarywave method, based on measurements of fluctuations in a ribbon-like interfacial
geometry, to determine the solid–liquid interfacial free energy for both polytypes of ice I and the
recently proposed ice 0 within a mono-atomic model of water. We discuss various choices for the
molecular order parameter, which distinguishes solid from liquid, and demonstrate the influence
of this choice on the interfacial stiffness. We quantify the influence of discretisation error when
sampling the interfacial profile and the limits on accuracy imposed by the assumption of quasi onedimensional
geometry. The interfacial free energies of the two ice I polytypes are indistinguishable
to within achievable statistical error and the small ambiguity which arises from the choice of order
parameter. In the case of ice 0, we find that the large surface unit cell for low index interfaces
constrains the width of the interfacial ribbon such that the accuracy of results is reduced. Nevertheless,
we establish that the interfacial free energy of ice 0 at its melting temperature is similar to that of
ice I under the same conditions. The rationality of a core–shell model for the nucleation of ice I
within ice 0 is questioned within the context of our results. © 2017 Author(s). All article content,
except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license
(http://creativecommons.org/licenses/by/4.0/). [http://dx.doi.org/10.1063/1.4975776]