UNLV physicists find water shifts to lower symmetry under extreme pressure

Physicists at UNLV reported Oct. 15, 2026, that water takes a lower-symmetry atomic form when squeezed to extreme pressure, in research published in Communications Chemistry.

The team squeezed water samples between two diamonds, the hardest known material, and checked the results with spectroscopy, which reads how matter absorbs and scatters light, plus X-rays that reveal atomic structure. The pressure reached 35 million pounds per square inch, compared with about 30 PSI in a car tire. The study, Evidence for symmetry-reduction in solid H2O above 222 gigapascals, appeared Oct. 15, 2026, in Communications Chemistry, a Nature Portfolio journal, with a DOI of 10.1038/s42004-026-02241-x, and authors from UNLV, the University of California, Berkeley, and Argonne National Laboratory.

Ordinarily, squeezing a material packs its atoms closer and raises symmetry, but water does not follow that pattern: its chemistry changes as pressure squeezes it, and its atomic arrangement drops to a lower symmetry. The result is a structure unlike anything water takes on Earth, and it would likely return to a familiar Earth form upon release.

UNLV frames the finding as evidence that water’s structure changes under conditions like those on other planets, altering its appearance and properties. Because researchers cannot enter a planet’s crust or atmosphere, they rely on Voyager program data about interior pressures and temperatures and copy the chemistry in laboratories instead.

A University of Rostock summary issued Jan. 13, 2026, described superionic water as an exotic, electricity-conducting solid that behaves partly like a liquid, with oxygen atoms locked in a rigid framework while hydrogen ions move freely through it. The experiments used the Matter in Extreme Conditions instrument at LCLS in the United States and the HED-HIBEF instrument at European XFEL. That research appeared in Nature Communications, with the paper published online Dec. 7, 2025.

The Rostock summary says the experiments squeezed water past 1.5 million atmospheres and heated it to thousands of degrees Celsius, capturing atomic-structure snapshots within trillionths of a second. StudyFinds reports 180 gigapascals, nearly 1.8 million times Earth’s atmospheric pressure, thousands of degrees, and 50-femtosecond X-ray pulses. Below 120 gigapascals two crystal structures coexisted, while above 150 gigapascals one arrangement dominated with 25 to 32 percent of the layers stacking differently.

At the lowest pressures studied, around 25 to 50 gigapascals, researchers found simpler, more orderly ice. Water forms at least 19 kinds of ice depending on pressure and temperature. Below 120 gigapascals both crystal arrangements cost nearly the same energy, so water genuinely cannot pick one.

The new high-precision experiments found a structure far messier than expected, combining face-centered cubic regions with hexagonal close-packed layers, different crystal patterns in which atoms stack in repeating geometries. Earlier research proposed either a body-centered cubic or a face-centered cubic oxygen arrangement, but the new work combines aspects of both. The results line up closely with the most advanced computer simulations, according to the University of Rostock.

The University of Rostock says the findings refine models of ice giant interiors and long-term evolution. The research team says superionic water could be the most abundant form of water by mass in the solar system. StudyFinds reports that Uranus and Neptune likely contain oceans of superionic water deep inside, where the flow of charged hydrogen ions through the oxygen lattice generates magnetic fields through dynamo action—moving conductive material creating a magnetic field—which may help explain the planets’ tilted, off-center magnetic fields. The team says the constraints should also aid ice giant formation models, which are common outside our solar system.

The superionic tests sandwiched water layers about half the width of a human hair between diamond windows and used laser pulses to generate shock waves. Each test lasted only nanoseconds and destroyed the target, so the team repeated the process many times. Timing ultrafast X-ray pulses with the shock compression produced diffraction patterns at far better resolution than earlier attempts, and machine learning simulations trained on quantum calculations matched the experimental patterns, confirming the disorder is real.

Funding came from a joint initiative between the German Research Foundation and the French research funding agency ANR, and more than 60 scientists from Europe and the US contributed. StudyFinds cites PROPICE grants ANR-22-CE92-0031 and DFG Project 505630685, plus U.S. Department of Energy Office of Science support for LCLS at SLAC and European XFEL proposal 4463.

Ashkan Salamat, the lab’s director and the study’s research lead, called researchers the initial pioneers trying to answer questions about these worlds in the laboratory. He also said water beyond Earth-like conditions behaves more complexly than imagined.