Size Effect on Nucleation Rate for Homogeneous Crystallization of Nanoscale Water Film

Abstract

The nucleation rate from classical nucleation theory is independent of sample size. In the past decades, several experimental and theoretical studies argued that the homogeneous nucleation rate of ice in supercooled droplets increases when the drop size is decreased. In this paper, we investigate the nucleation of ice in nanoscale water films using molecular dynamics simulations. We found that the nucleation rate of ice actually decreases when the film thickness decreases in the nanoscale regime. A theoretical model is presented to interpret the mechanism of nucleation rate decrease, which agrees well with the simulation results. The model divides films into the near-surface and the middle regions that are characterized by relatively low and high nucleation rates, respectively. The middle region dominates the nucleation process of films, whereas its effect is continuously weakened when increasing volume fraction of the near-surface region by decreasing the film size, leading to a decrease of the total nucleation rate. The structural and thermodynamic analyses indicate that the high stress induced by the surface layering slows down the diffusion and increases the nucleation barrier in the near-surface region, which is responsible for the low nucleation rate and eventually the decrease of the total nucleation rate.

Perspective: Surface freezing in water: A nexus of experiments and simulations

“…7b). A similar conclusion was reached in a work by Lü et al, who used a mean-first passage time (MFPT) method [136] to compute nucleation rates in films of different thicknesses [137]. Freestanding nanofilms have net zero curvature and are therefore not under Laplace pressure.…”

Effects of surface interactions on heterogeneous ice nucleation for a monatomic water model

“…12. Computer simulations can provide a route to understanding the microscopic mechanisms that govern heterogeneous ice nucleation without the difficulties of surface characterisation that can plague systematic experimental investigations. Several computer simulations of heterogeneous ice nucleation have been performed so far, including studying nucleation near a vapour interface, 13,14 on Lennard-Jones and kaolinite surfaces, 15,16 on metal surfaces, [17][18][19] in strong electric fields near surfaces, 20 in nanoscale pores, 21 and on graphitic surfaces, [22][23][24] and a considerable degree of insight has already been gained from such work. For example, it has been shown that surface roughness both at the molecular and nano-scale levels 22,24,25 appears to decrease the nucleation rate relative to a smooth surface; curvature likewise seems to lead to a reduction in the nucleation rate.…”

Distinct Properties of Nanofibrous Amorphous Ice

“…On one hand, the size distribution of the nanofibrous ices may result in two glass transitions due to size effects [32,33]. On the other hand, if the size effect is sufficiently enough to hinder the viscous state of water immediately after T g1 from crystallization [34], then the T g2 is related to the liquid-liquid transition of water [14]. …”