Enhanced heterogeneous ice nucleation by special surface geometry

Abstract

The freezing of water typically proceeds through impurity-mediated heterogeneous nucleation. Although non-planar geometry generically exists on the surfaces of ice nucleation centres, its role in nucleation remains poorly understood. Here we show that an atomically sharp, concave wedge can further promote ice nucleation with special wedge geometries. Our molecular analysis shows that significant enhancements of ice nucleation can emerge both when the geometry of a wedge matches the ice lattice and when such lattice match does not exist. In particular, a 45° wedge is found to greatly enhance ice nucleation by facilitating the formation of special topological defects that consequently catalyse the growth of regular ice. Our study not only highlights the active role of defects in nucleation but also suggests that the traditional concept of lattice match between a nucleation centre and crystalline lattice should be extended to include a broader match with metastable, non-crystalline structural motifs.

The Impact of Cloud Processing on the Ice Nucleation Abilities of Soot Particles at Cirrus Temperatures

“…While our DVS measurements were carried out at T =298 K, a change in contact angle could even be more pronounced at the subzero temperatures used for our cloud processing experiments, as the contact angle has been reported to decrease with T (Heydari et al., ). However, recent modeling studies suggest that soot hydrophilicity (contact angle) alone is not a good predictor for ice nucleation ability (Lupi & Molinero, ) but that cavities can promote the ice nucleation ability (Bi et al., ) through condensation and subsequent promotion of layering and ordering of supercooled liquid water ultimately triggering ice nucleation (on a molacular/interface level).…”

Interfacial Materials for Anti‐Icing: Beyond Superhydrophobic Surfaces

“…As displayed in Figure c, the ice‐nucleation rate enhancements at 70° and 110° wedge angles can be well explained by the matching of the wedge with the ice lattice . However, the promotion of ice nucleation at a 45° wedge is attributed to the formation of a special topological defect, which is an intermediate structure between liquid water and ice . That is, the HIN can be enhanced as long as the motion of the water is restricted and structurally compatible with a regular unit of ice .…”

“…Surface morphology has long been regarded as crucial for controlling ice nucleation . As displayed in Figure c, the ice‐nucleation rate enhancements at 70° and 110° wedge angles can be well explained by the matching of the wedge with the ice lattice . However, the promotion of ice nucleation at a 45° wedge is attributed to the formation of a special topological defect, which is an intermediate structure between liquid water and ice .…”

“…Reprinted (adapted) with permission from Ref. (Copyright 2017 Macmillan Publishers Ltd.). d) Effects of the NIBF and IBF surfaces on ice nucleation.…”

“…However, the promotion of ice nucleation at a 45° wedge is attributed to the formation of a special topological defect, which is an intermediate structure between liquid water and ice . That is, the HIN can be enhanced as long as the motion of the water is restricted and structurally compatible with a regular unit of ice . Hence, Li et al.…”