fahrbot-bot shares a report from Popular Mechanics: [I]n a new study published in the journal Nature Materials, scientists from the Korea Research Institute of Standards and Science (KRISS) have now found yet another phase, appropriately named Ice XXI. At the heart of the experiment, scientists used diamond anvil cells (DACs) — a common device used in materials science for squeezing samples under immense pressure — to subject water to 2 gigapascals (20,000 times higher than normal atmosphere) of pressure in just 10 milliseconds.
The scientists call this kind of water “supercompressed,” and it’s metastable, meaning it persists for a time even when another form of ice would be more stable. And because of the immense pressure, ice forms at room temperature but the molecules are much more densely packed. “Rapid compression of water allows it to remain liquid up to higher pressures, where it should have already crystallized to ice VI,” Geun Woo Lee, a co-author of the study from RISS, said in a press statement. “The structure in which liquid H2O crystallizes depends on the degree of supercompression of the liquid.”