Scientists at the University of Cambridge discovered that water in a single molecule layer does not act as a liquid or a solid, and that it becomes highly conductive at high pressures.
Much is known about the behavior of “bulk water”: it expands when it freezes, and it has a high boiling point. But when water is compressed to the nanoscale, its properties change dramatically.
By developing a new method for predicting this unusual behavior with unprecedented accuracy, researchers have discovered several new phases of water at the molecular level.
Water trapped between membranes or in tiny nanocavities is common – it can be found in everything from the membranes in our bodies to geological formations. But this nano-formed water behaves very differently from the water we drink.
To date, challenges of experimental characterization of water phases at the nanoscale have prevented a full understanding of its behavior. But in a paper published in the magazine temper nature، The Cambridge-led team describes how they used developments in computational approaches To predict the phase diagram of a thick layer of a single molecule of water with unprecedented accuracy.
They used a range of computational methods to enable the first principles level to be achieved for a single layer of water.
The researchers found that water confined to a thick layer of a single molecule goes through several phases, including a “hexagonal” phase and a “supra-ionic” phase. In the hexagonal phase, water acts as neither a solid nor a liquid, but rather as something in between. In the supra-ionic phase, which occurs at higher pressures, water becomes highly conductive, rapidly pushing protons through the ice in a manner similar to the flow of electrons in a conductor.
Understanding the behavior of water at the nanoscale is critical to many new technologies. The success of medical treatments can depend on how the water trapped in small cavities in our bodies interacts. The development of highly conductive electrolytes for batteries, water desalination, and frictionless fluid transportation depends on predicting how confined water will behave.
“For all of these areas, understanding the behavior of water is the key question,” said Dr. Venkat Kapil of the Cambridge Department of Chemistry Yusuf Hamid, first author of the research paper. “Our approach allows the study of a single layer of water in a graphene-like channel with unprecedented predictive accuracy.”
The researchers found that a single molecule thick layer of water within the nanochannel has a rich and diverse phase behavior. Their approach predicts several phases which include the hexagonal phase – an intermediate phase between a solid and a liquid – and also a super-ionic phase, in which water has high electrical conductivity.
“The hexagonal phase is neither a solid nor a liquid, but an intermediate, which is consistent with previous theories about two-dimensional materials,” Capel said. “Our approach also suggests that this phase can be seen experimentally by confining water in the graphene channel.
“The existence of the supra-ionic phase in easily accessible conditions is peculiar, as this phase is generally found in extreme conditions such as the cores of Uranus and Neptune. One way to visualize this phase is to oxygen atoms It forms a solid mesh, and the protons flow like a liquid through the mesh, like children running in a maze.”
The researchers say this super-ionic phase could be important for future electrolyte and battery materials because it exhibits electrical conductivity 100 to 1,000 times higher than current battery materials.
The results will not only help in understanding how to do it Water It works at the nanoscale, but also suggests that “nano-embedding” could be a new avenue for finding the supercoiling behavior of ions for other materials.
Angelos Michaelides, First Principles Phase Diagram of Ultrafine Monocrystalline Water, temper nature (2022). DOI: 10.1038 / s41586-022-05036-x. www.nature.com/articles/s41586-022-05036-x
the quote: New Phases of Water Discovery (2022, September 14) Retrieved September 14, 2022 from https://phys.org/news/2022-09-phases.html
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