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charon writes:

On the one hand, some scientists report success in creating solid metallic hydrogen (SMH):

Nearly a century after it was theorized, Harvard scientists have succeeded in creating the rarest - and potentially one of the most valuable - materials on the planet.

The material - atomic metallic hydrogen - was created by Thomas D. Cabot Professor of the Natural Sciences Isaac Silvera and post-doctoral fellow Ranga Dias. In addition to helping scientists answer fundamental questions about the nature of matter, the material is theorized to have a wide range of applications, including as a room-temperature superconductor. The creation of the rare material is described in a January 26 paper published in Science.

"This is the holy grail of high-pressure physics," Silvera said. "It's the first-ever sample of metallic hydrogen on Earth, so when you're looking at it, you're looking at something that's never existed before."

To create it, Silvera and Dias squeezed a tiny hydrogen sample at 495 gigapascal, or more than 71.7 million pounds-per-square inch - greater than the pressure at the center of the Earth. At those extreme pressures, Silvera explained, solid molecular hydrogen -which consists of molecules on the lattice sites of the solid - breaks down, and the tightly bound molecules dissociate to transforms into atomic hydrogen, which is a metal.

While the work offers an important new window into understanding the general properties of hydrogen, it also offers tantalizing hints at potentially revolutionary new materials.

Available on arXiv.org are both an abstract and a full article (pdf).

On the other hand, the journal Nature has an article which provides background on this report and then presents some arguments from scientists who still have some doubts:

[Continues...]

[...] It’s far from clear that the shiny material the researchers see is actually hydrogen, says geophysicist Alexander Goncharov of the Carnegie Institution for Science in Washington DC. Goncharov has criticized the Silvera lab’s methods before. He suggests that the shiny material may be alumina (aluminium oxide), which coats the tips of the diamonds in the anvil, and may behave differently under pressure.

Loubeyre and others think that Silvera and Dias are overestimating the pressure that they reached, by relying on an imprecise calibration between turns of the screw and pressure inside the anvil. Eugene Gregoryanz, a physicist at the University of Edinburgh, UK, adds that part of the problem is that the researchers took only a single detailed measurement of their sample at the highest pressure — making it hard to see how pressure shifted during the experiment.

“If they want to be convincing, they have to redo the measurement, really measuring the evolution of pressure,” says Loubeyre. “Then they have to show that, in this pressure range, the alumina is not becoming metallic.”

But Silvera says that he just wanted to get the news out there before making confirmation tests, which, he says, could break their precious specimen. “We wanted to publish this breakthrough event on this sample,” he says. To preserve the material, he and Dias have kept it in the cryostat; the lab has only two cryostats, and the other is in use for other experiments, he says. “Now that the paper has been accepted, we’re going to do further experiments.”

Inquiring minds want to know: are we there yet?

Original Submission