The new form, ice XXI, is structurally distinct from all previously known ice phases. It forms when water is rapidly compressed to supercompressed water<\/a> at room temperature.<\/p>\n The new phase is also metastable. This means it can exist for some time even though another form of ice would be more stable at those conditions. The results deepened the researchers\u2019 understanding of ice formation under high pressure.<\/p>\n \u201cRapid compression of water allows it to remain liquid up to higher pressures, where it should have already crystallized to ice VI,\u201d Geun Woo Lee, PhD, one of the scientists at KRISS, elaborated.<\/p>\n According to Lee, ice VI is particularly fascinating. Scientists believe it exists deep within icy moons like Titan and Ganymede<\/a>. Its highly distorted structure could enable complex transition pathways that lead to metastable ice phases.\u00a0<\/p>\n Unveiling ice XXI<\/p>\n For the research, the team used a diamond anvil cell, a device that can generate enormous pressures by squeezing a sample between two opposing diamonds, to recreate extreme planetary conditions. <\/p>\n Inside this cell, they compressed water up to two gigapascals (GPa), about 20,000 times more than normal air pressure. Under these pressures, water normally turns into ice VI<\/a>. However, when compressed extremely quickly, within just 10 milliseconds, the liquid remained stable long enough to transition into the newly observed ice XXI.<\/p>\n To capture the moment of crystallization, the team then turned to the European XFEL, whose ultrashort X-ray pulses can record atomic-scale events millions of times per second. <\/p>\n Like a high-speed camera, the XFEL enabled the scientists to film the rapid transformations as water molecules locked into their new arrangement.<\/p>\n<\/p>\n Follow-up experiments at the P02.2 beamline at PETRA III confirmed that ice XXI has a tetragonal crystal structure, built from surprisingly large repeating units known as unit cells.<\/p>\n \u201cWith the unique X-ray pulses of the European XFEL, we have uncovered multiple crystallization pathways in H2O, which was rapidly compressed and decompressed over 1000 times using a dynamic diamond anvil cell,\u201d Lee said. \u201cThe structure in which liquid H2O crystallizes depends on the degree of supercompression of the liquid.\u201d<\/p>\n Meanwhile, Cornelius Strohm, PhD, from the DESY HIBEF team, said samples are placed between the tips of two opposing diamond anvils in this specialized pressure cell. This allows them to be compressed precisely along a controlled pressure pathway.<\/p>\n \u201cIt is fantastic to see another great outcome from our Water Call, an initiative inviting scientists to propose innovative studies on water,\u201d Husband stated in a press release<\/a>. \u201cWe are looking forward to many more exciting discoveries ahead.\u201d<\/p>\n![\"\"](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2025\/10\/A2_9722fe.jpg\" "\\"World\u2019s")
Researchers led by scientists from the Korea Research Institute of Standards and Science (KRISS) have identified and described a new phase of ice called ice XXI.
Credit: European XFEL<\/a><\/p>\n