Ice Nucleation in Semiconfined Space Enclosed Partially by Nanosized Surfaces

While confined water generally exhibitsunique propertiesdifferentfrom its bulk counterpart, the semiconfined water, which is partiallyenclosed by finite-size surfaces and connected to the outside throughthe edges of the surfaces, displays distinctive behaviors. In thisstudy, we employed molecular dynamics simulation to investigate thefreezing of water semiconfined between two finite-sized nanoparticles.This work explores how the semiconfinement influences the ice nucleationof the enclosed water and the outside bulk water. Results indicatethat the semiconfinement can promote ice nucleation of the insidewater while the size of the confined surface is sufficiently large(e.g., >4 nm), and the separation of the confined surfaces is suitableto accommodate a few integers (e.g., 2-6) layers of ice. Wefound that the frozen inside water served as seeds to promote theice nucleation of outside bulk water. However, due to the contradictorycontribution of the separation of the two confined surfaces in facilitatingnucleation of the inside and the outside water, the semiconfinementcannot raise the freezing temperature of the outside water more than25 K in comparison with the homogeneous nucleation temperature. Furthermore,we also found that the two-dimensional bilayer or trilayer buckled(flat) ice formed inside the semiconfined space only slightly promotedthe ice nucleation of the outside water due to its too-small thickness,and the zigzag edge (or the primary prismatic plane) of the confinedbuckled ice layers is slightly more effective in promoting the icenucleation of outside water than the armchair edge (or the secondaryprismatic plane) of the confined ice layers. This study provides novelinsights into the freezing of the ubiquitous semiconfined water.

Automated summary

In this study, molecular dynamics simulation was used to investigate the freezing of water semiconfined between two finite-sized nanoparticles. The results show that semiconfinement can promote ice nucleation of the enclosed water, depending on the number of ice layers and the separation of the nanoparticles. The study also found that the frozen inside water serves as seeds to promote the ice nucleation of outside bulk water, but semiconfinement cannot significantly raise the freezing temperature of the outside water compared to homogeneous nucleation temperature.