Ice is a versatile substance that can take on a variety of forms depending on the conditions under which it crystallizes.

The most commonly known form of ice is referred to as ice I_h, which has a hexagonal lattice structure. However, there are several other types of ice structures that can form under specific conditions, with researchers having identified up to 20 different forms so far.

One such form of ice is cubic ice, also known as ice I_c, which was first believed to be the cause of a specific type of halo around the Sun or Moon a hundred years ago.

However, the existence of pure-phase ice I_c has been a topic of controversy for some time, given the difficulty in detecting it accurately in a significant number of experiments.

The Institute of Physics at the Chinese Academy of Sciences (CAS) has achieved a significant breakthrough in the study of ice. Through their research, they have confirmed the existence of pure-phase cubic ice in low-temperature interfaces, a discovery with far-reaching implications.

These groundbreaking findings have been published in Nature on March 29th, and they hold the potential to impact a diverse range of fields, from materials science to climate science.

Through the use of in-situ cryogenic transmission electron microscopy (TEM) imaging and water vapor deposition on graphene, researchers in this study were able to observe the formation of ice crystallites at a molecular level in real-time.

The results showed that the ice formed was pure-phase ice I, consisting mainly of single crystalline ice I_c with a small amount of ice I_h. The researchers were also able to demonstrate the preferential nucleation of ice I_c on low-temperature substrates. The polymorphic diversity of ice could be a possible explanation for the lack of prior detection of pure-phase ice by diffraction methods.

This discovery resolves the controversy surrounding cubic ice and marks a significant advancement in the fields of microscopy and ice physics. The implications of this research extend beyond these areas, as it enhances our understanding of ice formation under different conditions, with implications for fields such as materials science, geology, and climate science.

The National Science Foundation, the Ministry of Science and Technology of China, and the Youth Innovation Promotion Association of CAS provided support for this study.

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