Room-temperature ice invented

 Physics of water changed by discovery of Room-temperature ice by Scientists 

Scientists have created a new phase of ice that can form at room temperature but requires extreme levels of pressure. As per details available, it requires extreme levels of pressure to form. As its name suggests, it’s the twenty-first form of ice to have been identified, joining a fascinating array of other structures ranging from hexagonal and cubic to super ionic, which can be found on the surface of gas and ice giants like Neptune or Uranus. This new ice phase at room temperature have changed the physics of freezing. Finding doesn’t just expand our understanding of water’s strange behaviour, it may rewrite the very rules of how matter changes phase. It sounds like a paradox: ice that forms not in the cold, but in the comfort of room temperature. Yet this is exactly what a group of scientists has achieved. In an experiment that feels almost alchemical, researchers created a new form of ice, dubbed ice XXI, that emerges at room temperature when water is squeezed under unimaginable pressures. 

The finding shows just how many phases of water’s solid state there really are, and how much there’s still to learn about the extremely abundant stuff. The research could even help explain how extra-terrestrial forms of ice found on distant moons came to be. The experiment was spearheaded by the Korea Research Institute of Standards and Science (KRISS), in collaboration with European research facilities. Their setup involved an instrument known as a diamond anvil cell, which uses two precision-cut diamonds to compress water to extreme pressures, about 2 gigapascals, equivalent to roughly 20,000 times the normal atmospheric pressure. To capture what was happening on the atomic level, the team employed ultrashort X-ray bursts from the European XFEL, capable of taking microsecond-by-microsecond snapshots of molecules in motion. These images revealed that the water molecules, under pressure but still at room temperature, suddenly arranged themselves into a completely new crystal structure. This new structure, named ice XXI, exhibited a tetragonal lattice with an unusually large repeating unit containing 152 water molecules. It wasn’t simply frozen water; it was a novel molecular arrangement never before seen in nature or laboratory.

The research is a collaboration between Korea Research Institute of Standards and Science (KRISS) researcher Geun Woo Lee and scientists at the European X-Ray Free-Electron Laser Facility (XFEL), the world’s largest X-ray laser, and the German Electron Synchrotron (DESY) Research Centre. XXI ice forms when water is rapidly compressed to extraordinary levels at room temperature. It’s only stable under extremely specific conditions. It’s a major outlier in the group of almost two dozen forms of ice known to us, as most of them form at either high or low temperatures, according to the research. The researchers described ice XXI as metastable, a phase that can exist only under specific conditions and for short periods before reverting to a more stable form. This quality makes it a delicate but fascinating state of matter. By controlling the rate of compression and decompression, the scientists found that water could follow several different “paths” toward solidification. One of these rare routes led directly to the formation of ice XXI.

The experiment also showed that the speed of the pressure change was just as crucial as the pressure itself. When water is compressed quickly enough, it bypasses its usual freezing behaviour and transforms into entirely new configurations, something that defies classical thermodynamic models. This matters for planetary science, too. On icy moons like Europa, Ganymede and Enceladus, pressures deep below the surface can easily reach the levels required to form exotic ice phases. If ice XXI or similar structures exist in those environments, they could affect everything from planetary magnetism to the chemistry which supports potential life. Beyond planetary implications, the discovery forces scientists to reconsider the very nature of phase transitions. Traditionally, temperature and pressure have been viewed as the key levers which determine when a material melts, freezes or vaporizes. But ice XXI proves that timing and motion, how fast conditions change, can open new pathways into states of matter which classical physics does not predict. The implications of this breakthrough extend across physics, chemistry, and even astronomy. Water has always been seen as one of the most studied substances on Earth, yet its phase behaviour remains full of surprises. The discovery of ice XXI suggests that water’s 'phase diagram', the map that defines how it behaves under different conditions, may be far more complex than we imagined.

“Rapid compression of water allows it to remain liquid up to higher pressures, where it should have already crystallized to ice VI,” Lee explained, referring to a phase that is believed to be found in the interior of icy moons Titan and Ganymede. Put differently, XXI appears to be one possible intermediary stage between water and the exotic phase of ice found on distant icy moons. This insight has potential applications in materials science and engineering, where understanding non-equilibrium processes could lead to stronger, lighter, or more adaptable materials. For now, ice XXI is too unstable for practical use, but its discovery reveals a principle which may reshape how we think about creating matter on demand. Using a diamond anvil cell, a high-pressure device which have been used in materials science to recreate pressures present deep inside planets, the team observed what happened when water was put under two gigapascals of pressure, or roughly 20,000 times atmospheric air pressure. They then released the pressure over one second to see how the crystalline structures would react, before repeating the process hundreds of times. Despite being at room temperature, the water’s molecules packed together to form ice, albeit in a much more tightly packed structure.

The team then used the XFEL to capture images of the sample every microsecond, the equivalent of capturing footage with a high-speed camera, to watch how the ice structure formed. Even after centuries of study, water continues to surprise us. The same molecule which sustains life on Earth can, under the right conditions, transform into forms which seem to belong to another world. The discovery of ice XXI at room temperature is not just about freezing water, it’s about expanding our imagination of what is possible in physics. As one researcher said, “This isn’t just ice at room temperature, it’s a glimpse into how the universe plays with its own rules.” Ice, it turns out, doesn’t need to be cold to be extraordinary. “With 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,” Lee explained. “Our findings suggest that a greater number of high-temperature metastable ice phases and their associated transition pathways may exist, potentially offering new insights into the composition of icy moons,” co-author and DESY researcher Rachel Husband added.