Elucidating the role of vapor-liquid interfaces on ice nucleation

Vapor-liquid interfaces are known to accelerate heterogeneous ice nucleation at their vicinity, in a phenomenon known as contact freezing [1]. Their impact on homogeneous nucleation, however, is more ambiguous, as the experimental evidence for surface freezing [2], or enhancement of homogeneous nucleation at free interfaces, is not conclusive. Computational investigations of surface freezing also predict conflicting qualitative behaviors for different water models [3-4]. It has, however, been suggested that contact and surface freezing are related, as if a free interface can enhance heterogeneous nucleation, it must also have the same effect on homogeneous nucleation. In this work, we use forward-flux sampling [5] to explore this relationship, and observe that tetrahedral liquids undergoing surface freezing will also exhibit accelerated heterogenous nucleation kinetics when the crystal-nucleating agent is very close to the free interface. We attribute this finding to instabilities induced at a free interface due to the proximity of the nucleating surface.

1- A. J. Durant, Geophys Res Lett, 32, L20814 (2005).
2- A. Tabazadeh, PNAS, 99, 15873 (2002).
3- A. Haji-Akbari, PCCP, 16, 25916 (2014).
4- A. Haji-Akbari, PNAS, 114, 3316 (2017).
5- A. Haji-Akbari, JCP, 149, 072303 (2018).