ORNL scientists accidental creation of three otherworldly ice types challenges 35 years of ice research
While working on an experiment to create a super-cold state of water called amorphous ice, Oak Ridge National Laboratory scientists discovered a pathway to the unexpected formation of dense, crystalline phases of ice thought to exist beyond Earth’s limits.
“As ice changes phases, it’s similar to water going from a gas to a liquid to a solid except at low temperatures and high pressure—the ice transforms between various different solid forms,” said Chris Tulk, ORNL neutron scattering scientist and lead author.
Each known ice phase is characterized by its unique crystal structure at a particular temperature and pressure.
Scientists call the phase of earth's ice — whether it's at the North Pole or in your freezer — ice ih.
The new crystalline ice phases, known as ice IX, ice XV and ice VIII are three of at least 17 ice phases formed when molecules reorganize into crystalline structures at super-low temperatures and high pressures—conditions that don't naturally occur on earth.
The three otherworldy ice phases the scientists observed challenge accepted theories about super-cooled water and amorphous ice — a state of ice that forms with no ordered crystalline structure.
That's what Tulk and colleagues initially set out to study. The wanted to make amorphous ice, melt it and watch it recrystallize at higher pressures.
So, scientists froze water in a high-pressure device, cooling it to temperatures far below freezing and pressurizing it to nearly 4,600 times the pressure of an inflated car tire.
But after analyzing the data, they group was surprised to learn they had not created amorphous ice, but instead made three different ice types.
“If the data from our experiment was true, it would mean that amorphous ice is not related to liquid water but is rather an interrupted transformation between two crystalline phases, a major departure from widely accepted theory,” added Dennis Klug from the National Research Council of Canada, the lab that originally discovered the pressure-induced amorphization of ice in 1984.
At first, the team thought their observation was the result of a contaminated sample, so they conducted three more careful experiments, but got the same result.
Tulk said the findings place in doubt about 35 years of research on the relationship between pressure-induced amorphous ice and water. The researchers' findings will lead to better basic understanding of ice and its various phases found on other planets and moons and elsewhere in space, the lab said.
Source: Knoxville News Sentinel, by Brittany Crocker
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Published June 7, 2019