New form of ice discovered
Findings could have implications for our understanding of distant, water-
rich planets

Date:
March 18, 2022
Source:
University of Nevada, Las Vegas
Summary:
Researchers have discovered a new form of ice, redefining the
properties of water at high pressures.



FULL STORY ==========================================================================
UNLV researchers have discovered a new form of ice, redefining the
properties of water at high pressures.


========================================================================== Solid water, or ice, is like many other materials in that it can form
different solid materials based on variable temperature and pressure conditions, like carbon forming diamond or graphite. However, water is exceptional in this aspect as there are at least 20 solid forms of ice
known to us.

A team of scientists working in UNLV's Nevada Extreme Conditions Lab
pioneered a new method for measuring the properties of water under
high pressure. The water sample was first squeezed between the tips
of two opposite-facing diamonds -- freezing into several jumbled ice
crystals. The ice was then subjected to a laser-heating technique that temporarily melted it before it quickly re-formed into a powder-like
collection of tiny crystals.

By incrementally raising the 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 work which also demonstrated
that the transition to Ice-X, when water stiffens aggressively, occurs
at much lower pressures than previously thought.

While it's unlikely we'll find this new phase of ice anywhere on the
surface of Earth, it is likely a common ingredient within the mantle of
Earth as well as in large moons and water-rich planets outside of our
solar system.



==========================================================================
The team's findings were reported in the March 17 issue of the journal
Physical Review B.

Takeaways The research team had been working to understand the behavior
of high-pressure water that may be present in the interior of distant
planets.

To do so, Grande and UNLV physicist Ashkan Salamat placed a sample of
water between the tips of two round-cut diamonds known as diamond anvil
cells, a standard feature in the field of high pressure physics. Applying
a little bit of force to the diamonds enabled the researchers to recreate pressures as high as those found at the center of the Earth.

By squeezing the water sample between these diamonds, scientists drove
the oxygen and hydrogen atoms into a variety of different arrangements, including the newly discovered arrangement, Ice-VIIt.

Not only did the first-of-its-kind laser-heating technique allow
scientists to observe a new phase of water ice, but the team also found
that the transition to Ice-X occurred at pressures nearly three times
lower than previously thought -- at 300,000 atmospheres instead of 1
million. This transition has been a highly debated topic in the community
for several decades.

"Zach's work has demonstrated that this transformation to an ionic state
occurs at much, much lower pressures than ever thought before," Salamat
said. "It's the missing piece, and the most precise measurements ever on
water at these conditions." The work also recalibrates our understanding
of the composition of exoplanets, Salamat added. Researchers hypothesize
that the Ice-VIIt phase of ice could exist in abundance in the crust and
upper mantle of expected water-rich planets outside of our solar system, meaning they could have conditions habitable for life.


========================================================================== Story Source: Materials provided
by University_of_Nevada,_Las_Vegas. Original written by Natalie
Bruzda. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Zachary M. Grande, C. Huy Pham, Dean Smith, John H. Boisvert,
Chenliang
Huang, Jesse S. Smith, Nir Goldman, Jonathan L. Belof, Oliver
Tschauner, Jason H. Steffen, Ashkan Salamat. Pressure-driven
symmetry transitions in dense H2O ice. Physical Review B, 2022;
105 (10) DOI: 10.1103/ PhysRevB.105.104109 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220318170514.htm

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