New Phases of Water Found

New Phases of Water Found
New Phases of Water Found

Researchers from the University of Cambridge have found that water behaves neither as a liquid nor a solid in a single layer of molecules and becomes electrically conductive under extreme pressures.

Bulk water expands when frozen and has a high boiling temperature, two well-known properties. However, the properties of water change drastically when compressed at the nanoscale.

Researchers have discovered numerous new water phases at the molecular level, creating a brand new method to predict this strange behavior with unprecedented accuracy.

It is common to find trapped water between membranes or in small nanoscale spaces; Examples include membranes in our bodies and geological formations. But compared to the water we drink, this nano-enclosed water behaves quite differently.

The difficulties of experimentally describing the nanoscale phases of water have prevented its behavior from being fully known until now. But in a study published in the journal Nature, the Cambridge-led team describes how they were able to predict the phase diagram of a single-molecule-thick layer of water with extraordinary accuracy.

They combined computational approaches to provide first-principles level analysis of a single water layer.

Scientists have discovered that water, contained in a layer only one molecule thick, passes through a number of phases, including a "superionic" phase and a "hexatic" phase. Water behaves in the hexagonal phase, neither solid nor liquid, something in between.

At higher pressures, during the superionic phase, water becomes highly conductive and protons are rapidly pushed through the ice in a manner similar to the movement of electrons in a conductor.

Many emerging technologies depend on our ability to understand the behavior of water at the nanoscale.

Depending on how the water trapped in the tiny cavities of our bodies will react, medical treatments may or may not be effective. It is essential for the use of batteries to predict how closed water will behave, for desalination of water and for the creation of highly conductive electrolytes for frictionless fluid transmission.

The first author of the article is Dr. Yusuf Hamied from the Department of Chemistry, Cambridge. According to Venkat Kapil, understanding the behavior of water is the key issue in all these areas.

“With unmatched predictive precision, our method enables analysis of a single layer of water in a graphene-like channel,” he explains.

The researchers discovered that the single-molecular-thick water layer inside the nanochannel has a rich and varied phase behavior. Their method predicts a number of phases, including a superionic phase, where water has a high electrical conductivity, and the hexatic phase, which is an intermediary between a solid and a liquid.

Kapil said that, according to previous theories about two-dimensional materials, the hexagonal phase is an intermediate state that is neither solid nor liquid. According to our method, this step can also be observed in an experimental setting by introducing water into a graphene channel.

“Superionic phases are unusual because they typically only occur in extremely arid environments, such as the cores of planets like Uranus and Neptune. This phase can be imagined as a solid lattice of oxygen atoms and protons flowing through it like children navigating a liquid maze.”

The electrical conductivity of this superionic phase is 100-1000 times greater than that of current battery materials, according to the researchers, who believe it could be important for future electrolyte and battery materials.

The findings suggest that "nano-closure" could be a new method for describing superionic activity in other materials, as well as helping us understand how water behaves at the nanoscale.

source: phys.org

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