(659b) Theoretical and Computational Investigation of the Impact of Free 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 closely related phenomena because if a free interface is capable of enhancing heterogeneous nucleation at its vicinity, it must also have the same effect on homogeneous nucleation. In this work, we use our newly developed jumpy forward-flux sampling (jFFS) algorithm [5] and molecular dynamics (MD) simulations 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 sufficiently close to the free interface. By analyzing nucleation pathways, we identify a distinct “funneling” mechanism for situations in which heterogeneous nucleation is considerably accelerated. We are able to quantitatively explain these results by developing a simple CNT-based theoretical description of heterogeneous nucleation close to a free-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).