(39a) Contact Freezing Vs. Surface Freezing in Water

Contact freezing is a phenomenon in which heterogeneous ice nucleation occurs on a surface close to a vapor-liquid interface. In general, contact freezing is considerably faster than immersion freezing, i.e., heterogeneous nucleation on a surface fully immersed within the bulk [1-2]. Surface freezing, however, refers to the enhancement of homogeneous ice nucleation at or near a vapor-liquid interface [3]. Unlike contact freezing that is supported by direct experimental evidence, surface freezing is a more subtle phenomenon that is far more difficult to prove and characterize directly, and even though strong indications exist in its support, no direct experimental evidence for facilitation of homogeneous ice nucleation at vapor-liquid interfaces is available. Computational studies of surface freezing have also been inconclusive [4-5]. Contact freezing and surface freezing are conceptually related to one another as both involve nucleation close to a vapor-liquid interface. It has therefore been argued that the ability of a free interface to enhance heterogeneous nucleation (contact freezing) would also imply its propensity to facilitate homogeneous nucleation (surface freezing). This is, however, a speculation that has never been tested. The focus of this work is to test this hypothesis, by computing heterogeneous nucleation rates in several model tetrahedral liquids with known surface freezing propensities.

1- R. A. Shaw, et al., J. Phys. Chem. B, 109, 9865 (2005).

2- A. J. Durant, et al., Geophys. Res. Lett., 32, L20814 (2005).

3- A. Tabazadeh, et al., PNAS, 99, 15873 (2002).

4- A. Haji-Akbari, et al., Phys. Chem. Chem. Phys., 16, 25916 (2014).

5- A. Haji-Akbari, et al., PNAS, 114, 3316 (2017).