Researchers at UNLV have discovered a new form of ice, redefining the properties of water at high pressures.
Solid water, or ice, is similar to many other materials in that it can form different solid materials based on different temperature and pressure requirements, such as carbon forming diamond or graphite. However, water is exceptional in this aspect as there are at least 20 solid forms of ice which we know.
A team of scientists working in the UNLVs Nevada Extreme Conditions Lab pioneered a new method for measuring water''s properties under high pressure. The water sample was first squeezed between the sides of two opposite-facing diamondsfreezing into several jumbled ice crystals. The ice was then subjected to a laser-heating technique that temporarily melted it before it quickly re-form into a powder-like collection of tiny crystals.
By gradually increasing pressure and periodically blasting it with the laser beam, the team observed the water ice make the transition from a known cubic phase, Ice-VII, to the newly discovered intermediate, and tetragonal phase, Ice-VIIt, before settling into another known phase, Ice-X.
Zach Grande, a UNLV Ph.D. student, led the study, which further demonstrates that the transition to Ice-X, when water stiffens aggressively, is at significantly lower pressures than previously thought.
While it is unlikely to find this new phase of ice anywhere on Earth, it is likely to be a common ingredient within Earth''s mantle as well as in large moons and water-rich planets outside of our solar system.
The findings from the teams were revealed in the March 17 issue of the journal Physical Review B.
The research team had been working to understand the behavior of high-pressure water that may be present in distant locations.
Grande and UNLV physicist Ashkan Salamat secured a sample of water between the two round-cut diamonds known as diamond anvil cells, a common feature in high pressure physics. By applying a little force to the diamonds, the researchers simulated pressures as high as those found at the center of the Earth.
Scientists vetoed the oxygen and hydrogen atoms into a variety of different arrangements by squeezeing the water sample between these diamonds, including the newly discovered arrangement, Ice-VIIt.
The first-of-its-kind laser-heating technique allowed scientists to observe a fresh phase of water ice, but the team found that the transition to Ice-X occurred at pressures nearly three times lower than previously predicted at 300,000 atmospheres instead of 1 million. This transition has been a hot topic in the community for several decades.
According to Salamat, Zachs'' work has demonstrated that this transition to an ionic state has resulted in much lower pressures than ever before. It''s the missing piece, and the most precise measurements on water during these conditions.
A study reveals our understanding of the composition of exoplanets, according to Salamat. Researchers believe that the Ice-VIIt phase of ice might exist in abundance in the crust and upper mantle of predicted water-rich planets outside of our solar system, implying that they might have conditions acceptable for life.