In DepthHIGH-PRESSURE PHYSICS

Metallic hydrogen created in diamond vise

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Science  27 Jan 2017:
Vol. 355, Issue 6323, pp. 332-333
DOI: 10.1126/science.355.6323.332

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Summary

In 1935 a pair of physicists predicted that if the pressure of hydrogen were raised to about 250,000 times that of atmospheric pressure, it would turn into a solid metal. Experimentalists ever since have tried and failed to spot this transition, even after raising the pressure of hydrogen to millions of times atmospheric pressure. Now, the transition to solid metallic hydrogen may have been reached. Physicists in the United States say that by crushing a tiny amount of hydrogen between the tips of two flat-tipped diamonds at cryogenic temperatures they've raised the pressure to nearly 5 million times atmospheric pressure, causing the hydrogen to reflect light like a metal. They still don't have evidence the pressurized hydrogen is a solid. But even the claim that it is metallic is highly controversial. Other high-pressure physicists question some of the procedures used in the new study, and say they need more proof before they'll concede that the 80-year quest is over.