Gamingdeputy reported on May 23 that a research team composed of the School of Physics of Peking University and the Light Element Quantum Materials Cross-Platform (Light Element Platform) of Beijing Huairou Comprehensive National Science Center,Using the domestically developed qPlus scanning probe microscope, the atomic structure of the ice surface was “seen” for the first time in the world, and revealed the mystery of why it begins to melt at minus 153 degrees Celsius. The results were published in the international academic journal “Nature” on the evening of the 22nd.
Advertisement
The study of ice surface is of great significance for exploring the origin of life and the source of matter. However, due to the lack of atomic-scale experimental tools, the scientific community has not had a clear answer to the basic questions of ice surface structure.
Ice, as an important solid form of water, widely exists in nature. The global glacier area accounts for about one-tenth of the land area. Its surface often begins to melt at a temperature lower than its melting point (0°C). This phenomenon is called Pre-melting of ice.
The pre-melt phenomenon is helpful for humans to understand the lubrication phenomenon of the ice surface, the formation and lifespan of clouds, and the melting process of glaciers.International research currently generally believes that the temperature at which pre-melting occurs on the ice surface is above minus 70 degrees Celsius.
Advertisement
This study found that there are two stacking modes of hexagonal close-packing (Ih) and cubic close-packing (Ic) on the basal plane of hexagonal ice, which is different from the ideal ice surface that was generally believed to only have one stacking mode, Ih. The Ih and Ic crystal domains are connected through five- and eight-membered ring defects of water molecules, achieving seamless intra-layer stacking on the nanometer scale.
By precisely controlling the growth temperature and pressure of ice, the researchers discovered a long-range ordered periodic superstructure on the ice surface, in which Ic and Ih nanodomains of regular sizes were arranged alternately. By analyzing the distribution of hydrogen nuclei on the surface of the superstructure and combining it with first-principles calculations, the researchers found that this unique hydrogen bond network structure can significantly reduce the electrostatic repulsion energy between suspended hydrogen nuclei on the ice surface, making it more stable than an ideal ice surface.
This groundbreaking discovery refreshed people's traditional understanding of the ice surface and ended the long-standing debate on the surface structure and hydrogen order of ice.
According to reports, the team used the qPlus scanning probe microscope to develop an imaging technology that can distinguish hydrogen atoms and chemical bonds, and achieve accurate identification of the hydrogen bond network of water molecules on the ice surface and precise positioning of the distribution of hydrogen atoms. The detection found that the ice surface structure has both hexagonal close packing and cubic close packing, and the splicing and stacking form a stable network structure.
Professor Jiang Ying, head of the Light Element Platform, said: “We have ‘seen’ the pre-melting process of the ice surface on the atomic scale for the first time through temperature-changing experiments, and found that it begins to melt at minus 153 degrees Celsius. This is important for understanding the lubrication of the ice surface. Phenomenon, cloud formation and glacier melting process are very important.”
Gamingdeputy attached paper link: