Chinese Research Team Reveals Atomic Structure and Melting Mystery of Ice Surface
TapTechNews May 23rd news, a research team composed of the School of Physics, Peking University, and the Light Element Quantum Materials Interdisciplinary Platform of the Beijing Huairou Comprehensive National Science Center (referred to as the Light Element Platform) used the self-developed domestic qPlus-type scanning probe microscope to'see' the atomic structure of the ice surface for the first time internationally and revealed the mystery of its beginning to melt at minus 153 degrees Celsius. This achievement was published in the international academic journal Nature on the evening of the 22nd.
The research on the ice surface is of great significance for exploring the origin of life and the source of matter, but due to the lack of atomic-scale experimental tools, the basic questions about the ice surface structure in the scientific community have not been clearly answered.
As an important solid form of water, ice is widely present in nature. The global glacial area accounts for about one-tenth of the land area, and its surface often begins to melt at a temperature lower than its melting point (0°C), which is called the pre-melting of ice.
The pre-melting phenomenon is conducive to understanding phenomena such as the lubrication phenomenon of the ice surface, the formation and lifespan of clouds, and the ablation process of glaciers. International research currently generally believes that the temperature at which the ice surface undergoes pre-melting is above minus 70 degrees Celsius.
This study found that there are two stacking methods of hexagonal close-packed (Ih) and cubic close-packed (Ic) on the basal plane of hexagonal ice, which is different from the ideal ice surface that was generally considered to have only one stacking method of Ih in the past. Ih and Ic crystal domains are connected through five- and eight-membered ring defects of water molecules, achieving seamless intralayer stacking on the nanoscale.
By precisely controlling the growth temperature and pressure of the ice, the researchers discovered a long-range ordered periodic superstructure on the ice surface, in which regularly sized Ih and Ic nanocrystalline domains are alternately arranged; by analyzing the hydrogen nucleus distribution on the superstructure surface and combining with first-principles calculations, the researchers found that this unique hydrogen bond network structure can significantly reduce the electrostatic repulsive energy between the suspended hydrogen nuclei on the ice surface, making it more stable than the ideal ice surface.
This breakthrough discovery refreshes people's traditional perception of the ice surface and ends the long-term debate about the ice surface structure and hydrogen order.
According to the introduction, the team used the qPlus-type scanning probe microscope to develop an imaging technology that can distinguish hydrogen atoms and chemical bonds, rea lizing the accurate identification of the hydrogen bond network of water molecules on the ice surface and the precise positioning of hydrogen atom distribution. The detection found that there are two arrangement methods of hexagonal close-packed and cubic close-packed on the ice surface structure at the same time, and they are spliced and stacked to form a stable network structure.
Professor Jiang Ying, the head of the Light Element Platform, said: 'Through variable temperature experiments, we first'saw' the process of pre-melting on the ice surface at the atomic scale and found that it begins to melt at minus 153 degrees Celsius, which is crucial for understanding phenomena such as the lubrication of the ice surface, the formation of clouds, and the ablation process of glaciers'.
TapTechNews attached the paper link:
https://www.nature.com/articles/s41586-024-07427-8