[meteorite-list] Scientists Predict an Out-of-this-world Kind of Ice

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 17 Jan 2012 12:16:41 -0800 (PST)
Message-ID: <201201172016.q0HKGfOT022651_at_zagami.jpl.nasa.gov>

http://www.news.cornell.edu/stories/Jan12/NewIce.html

Scientists predict an out-of-this-world kind of ice

Cornell scientists are boldly going where no water molecule has gone
before -- that is, when it comes to pressures found nowhere on Earth.

By Anne Ju (amj8 at cornell.edu)
Cornell University
January 16, 2012

Exploring what Cornell's Neil Ashcroft calls the "utterly fundamental"
transition from insulating to conducting, or metallic, matter, the
researchers have combined high-powered computing and "chemical
intuition" to discover new phases of water -- specifically, ice at
extremely high pressures nonexistent on Earth but probably abundant
elsewhere in the solar system.

The research, published online Dec. 29 in Proceedings of the National
Academy of Sciences, was conducted by Ashcroft, the Horace White
Professor of Physics Emeritus; Roald Hoffmann, the 1981 chemistry Nobel
laureate and Frank H.T. Rhodes Professor in Humane Letters Emeritus;
and Andreas Hermann, a postdoctoral associate in chemistry and physics.

Combining their interests in condensed matter physics, the discovery of
new chemistries and high-pressure studies of water, the researchers
predict a sequence of never-before-seen, stable structures of ice in
the 1-5 terapascal pressure range. In terrestrial terms, pressure is
expressed in atmospheres (we live under one atmosphere of pressure). A
terapascal (TPa) is 10 million atmospheres.

"This pressure is way above anything that can be done in the
laboratory," Hoffmann said. "It certainly can't be found in Ithaca, not
even at Lynah Rink during the Harvard game." It is, however, in the
range of the pressure regimes on Uranus and Neptune -- planets whose
major components include, well, ice. This means that these far-fetched
phases of ice might not just be theories -- they are probably what you
would find if you could descend toward the core of the outer planets of
our solar system, or in the center of extra-solar planets being
discovered today.

So what does ice do at these pressure scales? Discrete water molecules
disappear; the H2O in the new ices has an extended network of oxygens
and hydrogens. Like sardines in a can, the oxygen-hydrogen-oxygen bonds
get squeezed together, forming new shapes. The new ices eventually
become metals, but not as quickly as others had previously thought.
Researchers at other universities (who inspired the Cornell
researchers) have described ice phases that became metallic at
pressures higher than 1,550 gigapascals (1 gigapascal is 10,000
atmospheres).

The Cornell researchers' calculations predict new phases stable at
pressures above 1 TPa, but the most stable new ices will be insulating
-- not metallic -- pushing the theoretical transition pressure for
metallization of ice beyond 4.8 TPa.

Their calculations also point to evidence that, in fact, in those
extreme pressure regimes, ice might become squeezed to the point of
transforming into a quantum liquid -- a most unusual intimation, they
said.

"It's hard to imagine -- pressure-induced melting of bulk ice,"
Ashcroft said.

The research was supported by the Department of Energy and the National
Science Foundation, and the computational work was done on the TeraGrid
network provided by the National Center for Supercomputer Applications
and the Cornell NanoScale Facility.
Received on Tue 17 Jan 2012 03:16:41 PM PST