First Formation Of Metallic Hydrogen

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First Formation Of Metallic Hydrogen

#1  Postby Calilasseia » Jan 30, 2017 5:14 pm

Scientists at Harvard University have reported the first formation of metallic hydrogen in the laboratory. New Scientist covers the finding here, whilst Science has published the paper here.

Citation:

Observation Of The Wigner-Huntingdon Transition To Metallic Hydrogen by Ranga P. Dias & Issac F. Silvera, Science, DOI: 10.1126/science.aal1579 (26th January 2017)

Dias & Silvera, 2017 wrote:Abstract

Producing metallic hydrogen has been a great challenge to condensed matter physics. Metallic hydrogen may be a room temperature superconductor and metastable when the pressure is released and could have an important impact on energy and rocketry. We have studied solid molecular hydrogen under pressure at low temperatures. At a pressure of 495 GPa hydrogen becomes metallic with reflectivity as high as 0.91. We fit the reflectance using a Drude free electron model to determine the plasma frequency of 32.5 ± 2.1 eV at T = 5.5 K, with a corresponding electron carrier density of 7.7 ± 1.1 × 1023 particles/cm3, consistent with theoretical estimates of the atomic density. The properties are those of an atomic metal. We have produced the Wigner-Huntington dissociative transition to atomic metallic hydrogen in the laboratory.
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Re: First Formation Of Metallic Hydrogen

#2  Postby Thommo » Jan 30, 2017 5:23 pm

I saw this a few days ago and was interested enough to start making a thread, but the further I got with looking for sources to explain what was going on the more it seemed that there was a lot of reason to doubt the claim. Putting the case for why it might be more accurate to suggest "scientists haven't made metallic hydrogen" in layman's terms I found a fair few articles like these:-

http://www.forbes.com/sites/samlemonick ... 909edd1ae2

http://www.independent.co.uk/news/scien ... 49056.html
five different experts have told Nature's news reporters that they don't believe the claim and that it could be based on an error. One scientist told the news organisation that the paper isn't “convincing at all”.


http://www.nature.com/news/physicists-d ... en-1.21379
other researchers have serious doubts about the claim, the latest in a field with a long history of failed attempts.


http://gizmodo.com/did-scientists-actua ... 1791694091
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Re: First Formation Of Metallic Hydrogen

#3  Postby newolder » Jan 30, 2017 5:37 pm

The BBC report contains a scathing indictment...
...
"Complete garbage," is how Eugene Gregoryanz from Edinburgh University described the research. "Like everybody else who works with hydrogen at high pressures, I am appalled by what is being published in Science."
...
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Re: First Formation Of Metallic Hydrogen

#4  Postby JoeB » Jan 31, 2017 11:00 am



This is a nice presentation about the alleged discovery, and its use.
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Re: First Formation Of Metallic Hydrogen

#5  Postby lpetrich » Feb 11, 2017 6:32 am

I've found stuff on other nonmetal-metal transitions:

Xe: 1.4 Mbar (140 GPa), CsI: 1.1 Mbar (110 GPa), I2 (17 GPa, monatomic at 21 GPa), NiI, N2 (pred. 194 GPa), O2, Br, CaH2 (pred. 138 GPa), H2O (>4.8 TPa?), CS2 (pred. 50 GPa), He (pred. 0 K: 10 TPa, 20,000 K: 3 TPa), H (10^3 K: ~140 GPa, 0 K: > 400 GPa)

I've found Pressure-Induced Insulator-Metal Transition - Springer and The Physics of Phase Transitions: Concepts and Applications - Pierre Papon, Jacques Leblond, Paul H.E. Meijer - Google Books, but they are both paywalled.

The existence of a metal-like degenerate matter implies that every (condensed) nonmetal has some pressure that makes it a metal. In fact, metals may be interpreted as low-pressure degenerate matter.
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Re: First Formation Of Metallic Hydrogen

#6  Postby DavidMcC » Feb 12, 2017 1:56 pm

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Re: First Formation Of Metallic Hydrogen

#7  Postby DavidMcC » Feb 15, 2017 7:27 pm

What degeneracy means in solid state electronics is the number of particles (typically electrons) that can occupy the same spatial state. Since electons are spin-1/2 particles (with just two spin states, up and down), the degeneracy of any electronic spatial state is 2.
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Re: First Formation Of Metallic Hydrogen

#8  Postby DavidMcC » Feb 17, 2017 1:03 pm

BTW, most electron states within atoms and ions are not degenerate, because spin-orbit coupling splits the levels.
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Re: First Formation Of Metallic Hydrogen

#9  Postby lpetrich » Feb 18, 2017 6:37 pm

They split into states with different total angular momentum, and those states can be degenerate.
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Re: First Formation Of Metallic Hydrogen

#10  Postby DavidMcC » Feb 18, 2017 6:56 pm

lpetrich wrote:They split into states with different total angular momentum, and those states can be degenerate.

That is a different splitting, and I would agree that that split is often degenerate, but that was not my claim, which concerned electronic spin-orbit coupling only.
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Re: First Formation Of Metallic Hydrogen

#11  Postby newolder » Feb 24, 2017 5:57 pm

The only sample of metallic hydrogen on Earth has vanished.

The physics world was abuzz with excitement (and skepticism) last month when scientists from Harvard University claimed they had created a stable sample of metallic hydrogen. Their initial testing and paper garnered a great deal of interest, as no one had thus far been able to prove the theoretical material existed. The team said more testing would be done to confirm the material was indeed the fabled new form of hydrogen, but they now report the sample has vanished... [more at link]

:doh:
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Re: First Formation Of Metallic Hydrogen

#12  Postby DavidMcC » Feb 26, 2017 2:39 pm

It may still be intact someplace in the equipment, or it could have returned to a gaseous state.

I don't see how it can still be intact (as metal), it must have returned to the vapour phase. I don't see any other thermodynamically feasible outcome of loss of pressure.
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Re: First Formation Of Metallic Hydrogen

#13  Postby crank » Feb 26, 2017 10:35 pm

lpetrich wrote:I've found stuff on other nonmetal-metal transitions:

Xe: 1.4 Mbar (140 GPa), CsI: 1.1 Mbar (110 GPa), I2 (17 GPa, monatomic at 21 GPa), NiI, N2 (pred. 194 GPa), O2, Br, CaH2 (pred. 138 GPa), H2O (>4.8 TPa?), CS2 (pred. 50 GPa), He (pred. 0 K: 10 TPa, 20,000 K: 3 TPa), H (10^3 K: ~140 GPa, 0 K: > 400 GPa)

I've found Pressure-Induced Insulator-Metal Transition - Springer and The Physics of Phase Transitions: Concepts and Applications - Pierre Papon, Jacques Leblond, Paul H.E. Meijer - Google Books, but they are both paywalled.

The existence of a metal-like degenerate matter implies that every (condensed) nonmetal has some pressure that makes it a metal. In fact, metals may be interpreted as low-pressure degenerate matter.

Some of these transition should never ever EVER have been allowed!

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Re: First Formation Of Metallic Hydrogen

#14  Postby DavidMcC » Feb 27, 2017 12:56 pm

I'd like to know how the authors quoted by the NS article think that metallic hydrogen can continue to exist after the presssure has ben taken off. Perhaps they are thinking of the formation of diamond from graphite at vey high T and P, which certainly does survive the loss of high T and P. However, the difference between graphite and diamond is only in the C-C bonds - ie, the outer, valence electrons - the inner electronic orbitals are essentially unaffected, whereas the difference between gaseous H and metallic H is that the orbitals themselves are being compressed in metallic H, so when this compression is released, the orbitals must return to their normal size.

EDIT: I see that the science article says that metallic H is expected to be metastable when the pressure is released. I'd like to know the potential barrier creating this metastability. I suspect that it would be low, making it very like instability.
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Re: First Formation Of Metallic Hydrogen

#15  Postby DavidMcC » Feb 27, 2017 1:28 pm

Presumably, the experiment will be reproduced, but next time, they will reduce the pressure in a cntrolled way as soon as the metallic form has been observed, so that they can actually observe what happens to the ball of metal at reduced pressure.
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