Experiment offers glimpse at how to make hydrogen metallic

A crushing squeeze between diamonds has pushed hydrogen to the brink of morphing into a metal. Scientists in Scotland and China discovered a new solid phase of hydrogen after subjecting the universe’s most abundant element to pressures that dwarf the water pressure at the ocean floor. The researchers speculate that slightly more pressure may coax hydrogen to take on a solid, metallic form first predicted 81 years ago.

In nature, pairs of hydrogen atoms bond tightly to form the molecule H₂. But with enough pressure, the bonds should break, allowing electrons to flow freely past individual atoms as they do in metals.

The researchers found that at pressures between about 3.2 million and 3.8 million times as high as the atmospheric pressure at sea level, the hydrogen seemed to exist as a part-molecular, part-atomic layer cake. As little as a several percent boost in pressure could coax the rest of the sample to turn metallic, the researchers suggest online January 6 in Nature, though they warn that diamonds may not be able to do the job.

Metallic hydrogen could have special properties, such as the ability to conduct electric current with no resistance at room temperature. Plus, it should stay intact once created, just as a diamond survives above ground even though it requires crushing pressure to form.