The diamond resists even a grip. Surprisingly, the structure of the material persists even when compressed to 2 trillion pascals, more than five times the pressure in the Earth’s core, scientists reported on Jan. 27 in Nature.
The study suggests that diamond is metastable at high pressures: it maintains its structure even though other more stable structures are expected to dominate under these conditions. Studying the peculiarities of diamond at extreme pressures could help reveal the internal workings of carbon-rich exoplanets (SN: 16/07/14).
Diamond is one of several varieties of carbon, each composed of a different arrangement of atoms. At daily pressure on the Earth's surface, the most stable state of carbon is graphite. But given strong pressure, the diamond wins. This is why diamonds are formed after carbon has plunged into the Earth.
But at higher pressures than those found inside the Earth, scientists had predicted that the new crystal structures would be more stable. Then physicist Amy Lazicki and colleagues beat diamonds with powerful lasers at the Lawrence Livermore National Laboratory Ignition Facility in California. X-ray measurements of the material structure revealed that the diamond persisted, suggesting that it is metastable under extreme pressure.
It was already known that diamond was metastable at low pressures: your grandmother’s diamond ring did not turn into graphite. Once formed, the structure of the diamond can persist even if the pressure is low, thanks to the strong chemical bonds that bind the carbon atoms in the diamond. Now, says Lawrence Livermore's Lazicki, "it seems like the same thing happens when a lot more pressure is pressed."