Metal Becomes Transparent Under High Pressure

Mar 12, 2009
Sodium, a white metal at pressures below 1.5 Mbar (left -- picture at 1.1 Mbar, 1 Mbar = 1 million atmospheres), turns black at 1.5 Mbar (center -- picture at 1.56 Mbar) and becomes red transparent at 1.9 Mbar (right -- picture at 1.99 Mbar). It is predicted to become colorless and transparent like glass at ~3 Mbar.

An international team of scientists have discovered a transparent form of the element sodium (Na). The team, led by Artem Oganov, Professor of Theoretical Crystallography at Stony Brook University, and Yanming Ma, the lead author and professor of physics at Jilin University in China, was able to demonstrate that sodium defies normal physical expectations by going transparent under pressure. The results are published in the March 12 edition of the journal Nature.

“It is well known that at sufficiently high compression all materials must go metallic,” said Oganov. “This is seen in the metallization of hydrogen at high pressures and temperatures inside planets Jupiter and Saturn.”

However, as the researchers found, element does just the opposite. A perfect white metal at atmospheric , on increasing pressure sodium first turns black, then (at the pressure of 2 million atmospheres) red transparent, and eventually becomes a colorless - just like glass.

“This fundamental result is important for understanding properties of highly compressed matter, particularly within stars and ,” said Oganov.

The unexpected transformation was first predicted by Professor Ma. His sophisticated calculations clearly indicated that sodium adopts unusual crystal structures and becomes an insulator at high pressures. Together with Professor Oganov, Ma was able to demonstrate that, at very high compressions, overlapping sodium atoms force their into the “holes” between the atoms.

“In these holes electrons demonstrate an extremely localized behavior, responsible for the collapse of the ,” said Ma. “These electrons behave as ‘fake atoms,’ just like in electrides - where the role of the anion is played by localized electrons.”

To test this unexpected prediction, Ma and Oganov contacted Mikhail Eremets, the leader of an experimental group at Max Planck Institute of Chemistry, Mainz (Germany). Eremets was initially skeptical of the Ma-Oganov predictions, yet he was undeterred by extreme technical challenges of reaching pressures of over 2 million atmospheres. Eremets and his group initiated a cohort of several extremely difficult experiments, using a tiny micrometer-size sample. Through these experiments, the group was able to confirm the predictions of a new structure and transparency of sodium (see Figure).

“What fascinated us most is that the pressures at which this transformation was predicted were experimentally reachable,” Oganov said, “and that at these conditions such a remarkable change of chemistry occurs”.

Provided by Stony Brook University

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User comments : 9

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SciTechdude
3.3 / 5 (10) Mar 12, 2009
Save the whales with your transparent sodium fish tank in your spacecraft! Yay!
Mercury_01
Mar 12, 2009
This comment has been removed by a moderator.
pseudophonist
4.5 / 5 (4) Mar 13, 2009
This is totally fake.

Actually its very believable since most of our scientific knowledge is based around 1atmosphere.
Alexa
2.6 / 5 (5) Mar 13, 2009
I'm missing an information, when we could expect first sun glasses made of transparent sodium?
tkjtkj
1 / 5 (4) Mar 13, 2009
"It is predicted to become colorless and transparent like glass at ~3 Mbar."

Well, what is going on here!? Is this a prediction?? or an observation??? There IS a difference, you know!

How do articles like this get into the press!? Are they not edited for clarity? And why must i even ask about this? Can't it be expected that an article 'speaks for itself'??

raron
3.7 / 5 (3) Mar 13, 2009
SciTechdude: lol. They almost got it right. Thats the funniest Star Trek movie btw!
docatomic
3 / 5 (2) Mar 13, 2009
Ah, yes; of course - the initial discovery of superinsulators.
Alexa
3 / 5 (1) Mar 13, 2009
"It is predicted to become colorless and transparent like glass at ~3 Mbar." Well, what is going on here!? Is this a prediction??
Usage of "predicted" word usually denotes a prediction - or am I wrong?
Mercury_01
1 / 5 (4) Mar 13, 2009
This is totally fake.

Actually its very believable since most of our scientific knowledge is based around 1atmosphere.


Its called bullshitting. try it out sometime.
andrzejmiklaszewski
not rated yet Mar 17, 2009
I'm wondering about the pressure, which method was used to get so big amount??the authors only suggesting the small size of sample