Recently is been reported than metallic hydrogen has been observed in the laboratory at a pressure of around 4,890,000 atm. This as far as I know is even greater than Earth's core theorized pressure. How did they make to create such pressure in laboratory?
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3-1. No research effort.If you find out where it is reported, you will probably find out how they did it. You should not expect us to do your research for you. – sammy gerbil Jan 28 '17 at 20:16
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1They use synthetic diamonds to squeeze a tiny sample. There is another question on today's page with links, http://physics.stackexchange.com/q/308155/ – Jan 28 '17 at 20:44
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2Possible duplicate of For the recently reported production (January 2017) of metallic hydrogen in the laboratory - what is the evidence exactly? – John Rennie Jan 29 '17 at 08:09
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Why is the pressure at the Earth's core meaningful at all as a benchmark of what can or cannot be achieved in the lab? – Emilio Pisanty Feb 01 '17 at 15:33
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I don't think this is a duplicate. The dupe was asking about the observation of metallic hydrogen - this is asking about the mechanism for making a high pressure. – Floris Feb 03 '17 at 17:09
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It's an interesting question - and one that a little searching will help answer.
From the New Scientist article on this finding:
When Silvera and Dias managed to turn hydrogen metallic, it was at a pressure of 495 GPa, well beyond the 360 GPa of Earth’s core.
They were able to obtain such a high pressure by crushing the solid hydrogen between the flattened tips of two synthetic diamonds. To prevent the diamonds from cracking, the tips were carefully polished to remove surface defects, heated to remove any residual internal stresses, and coated in alumina, an extremely hard compound of aluminium and oxygen that hydrogen can’t seep through.
Depending on what source you believe, the yield stress of diamond is around 60 GPa - with some sources claiming values up to 225 GPa in some orientations. That is well below the 495 GPa claimed in the article. But that may be related to microscopic flaws in the diamond - in particular, tiny surface cracks. It may be that the yield strengths for diamond reported elsewhere assume that these cracks cannot be avoided, and present a natural limit to the strength. But according to the report in the Harvard magazine:
Diamonds, including the nearly perfect synthetic specimens used in the anvil, are the hardest substances on Earth, but at the pressures needed to create metallic hydrogen—almost 5 million atmospheres—they frequently break. The researchers therefore had to overcome three principal causes of these experiment-ending fractures.
Minute surface imperfections can cause the gems to break along the flaws, the way window glass breaks where it has been scored. “A polished diamond under a microscope looks beautiful,” Silvera explained in an interview, “but if you use atomic force microscopy, you see little defects. And if that is on the culet, the part that is pushing on the hydrogen, and it is highly stressed, it can break there.” His research group was able to etch away these nanoscale imperfections using a reactive ion etching technique available through Harvard’s Center for Nanoscale Systems.
A second problem has to do with the hydrogen molecule itself. Hydrogen is “the simplest and most fundamental atom, a single proton with an electron,” Silvera pointed out. And because it is so small, it can actually diffuse, even in the molecular form, under the intense pressures created in the anvil, into the molecular crystalline lattice of the diamonds themselves, breaking them apart. The researchers responded by coating the stones with a thin layer of alumina, which acts as a diffusion barrier against hydrogen.
Silvera also knew that diamonds become brittle when exposed to laser light under high pressure: a colleague at Cornell, Arthur Ruoff, had told him about breaking 15 sets of diamonds by shining lasers into them to study the properties of hydrogen at about 3.5 million atmospheres of pressure. So Silvera and Dias, operating at even higher pressures, took care never to shine a high-power laser into their sample.
Several physicists have expressed skepticism [...]
