Molecular-Resolution Imaging of Ice Crystallized from Liquid Water

TL;DR

This study achieves molecular-resolution imaging of ice crystallized from liquid water using cryogenic electron microscopy, revealing defect structures and dynamic behaviors at the nanoscale.

Contribution

Development of cryogenic liquid-cell TEM for angstrom-resolution imaging of ice, enabling direct observation of defect structures and dynamic processes during crystallization.

Findings

Ice formation tolerates nanoscale defects like misoriented subdomains and gas bubbles.

Bubble surfaces form low-energy nanofacets with minimal strain in the crystal.

Bubbles can nucleate, grow, migrate, dissolve, and coalesce under electron irradiation.

Abstract

Despite the ubiquity of ice, a molecular-resolution image of ice crystallized from liquid water or the resulting defect structure has never been obtained. Here, we report the stabilization and angstrom-resolution electron imaging of ice Ih crystallized from liquid water by developing cryogenic liquid-cell transmission electron microscopy (CRYOLIC-TEM). We combine lattice mapping with molecular dynamics simulations to reveal that ice formation is highly tolerant to nanoscale defects such as misoriented subdomains and trapped gas bubbles, which are stabilized by molecular-scale structural motifs. Importantly, bubble surfaces adopt low-energy nanofacets and create negligible strain fields in the surrounding crystal. These bubbles can dynamically nucleate, grow, migrate, dissolve, and coalesce under electron irradiation and be monitored in situ near a steady state. This work opens the door to understanding water crystallization behaviors at an unprecedented spatial resolution.