Bold claim: Atoms can stand still inside a molten metal, reshaping how we think about liquids turning into solids. Researchers have uncovered that, within a liquid, some atoms remain fixed in place even under extreme heat. These motionless atoms exert a powerful influence on solidification, including the emergence of an unusual state called a corralled supercooled liquid.
Why this matters: How materials solidify is central to many natural processes—minerals forming, ice developing, and proteins folding. It also underpins technologies across medicine, metals, aviation, construction, and electronics.
Watching molten metal form at the smallest scales
A team from the University of Nottingham and the University of Ulm used transmission electron microscopy to watch molten metal droplets shrink and solidify. Their observations, published on December 9 in ACS Nano, reveal surprising details about atomic motion during solidification.
What happens in liquids is complex
In liquids, atoms move in a crowded, ever-changing dance, slipping past one another at high speeds while still influencing nearby atoms. Capturing this motion is particularly challenging during the crucial moment when a liquid starts to become a solid, a process that sets the resulting material’s structure and properties.
A novel experimental setup and a surprising finding
Dr. Christopher Leist, who conducted the low-voltage SALVE electron microscopy experiments in Ulm, melted metal nanoparticles (platinum, gold, palladium) that rested on graphene. Graphene served as a tiny heater, or a “hob,” to warm the particles. As they melted, the atoms moved rapidly—as expected—but some atoms stayed fixed.
Further analysis showed that these stationary atoms form strong bonds with specific spots on the graphene support known as point defects. Moreover, by focusing the electron beam on selected regions, the researchers created more defects and could tune how many atoms remained pinned in the liquid.
A dual nature of electrons leads to a new phase
Professor Ute Kaiser, who established the SALVE center at Ulm, explains that the experiment directly showcases the wave–particle duality of electrons: electrons act like waves when imaging the material, but they also behave like particles delivering bursts of momentum that can move or pin atoms at the edge of a liquid metal. This combination enabled the team to identify what they describe as a new phase of matter.
This same group has previously captured real-time images of chemical bonds breaking and reforming, demonstrating that chemistry can unfold at the level of single atoms.
Atomic corrals steer crystal growth
The study shows that stationary atoms can dramatically shape how a liquid crystallizes. If only a few atoms are pinned, crystals can grow from the liquid and eventually solidify the entire nanoparticle. If many atoms are pinned, crystal formation can be hindered or entirely blocked.
A striking scenario occurs when stationary atoms form a ring around the liquid, creating an atomic corral. With the liquid trapped inside, it can remain liquid well below its usual freezing point—for platinum, as low as 350°C, which is more than 1,000°C cooler than expected.
When conditions allow, the corralled liquid eventually freezes, but not into a regular crystal. Instead, it becomes an amorphous solid—an unstable, non-crystalline metal held in that state by the surrounding pinned atoms. If the confinement weakens, the material relaxes its stress and reverts to a normal crystalline structure.
A new hybrid metal state with catalytic implications
Catalysis expert Dr. Jesum Alves Fernandes notes that discovering a confined liquid state with non-classical behavior could alter how we understand catalysts. Platinum on carbon is a cornerstone of many catalytic processes, so this confined-liquid phase could inspire smarter, longer-lasting, and self-cleaning catalysts.
Toward new forms of matter and cleaner technologies
Until now, corralling effects have been demonstrated primarily for photons and electrons. This research shows that atoms themselves can be corralled, hinting at a possible new material class that blends solid- and liquid-like traits in a single substance.
By arranging pinned-atom patterns on surfaces, scientists may build larger, more intricate atomic corrals. Such control over rare metals could improve how we use precious materials in clean energy technologies, including energy conversion and storage.
Funding and outlook
This work was supported by the EPSRC Program Grant “Metal atoms on surfaces and interfaces (MASI) for sustainable future.”
What this means for science and society
- Controlling atomic motion inside liquids could lead to better understanding and design of materials, from catalysts to advanced metals.
- The idea of a corralled, hybrid metal state invites questions about stability, scalability, and practical applications in industry.
- As with any controversial claim in materials science, opinions vary on how broadly this corralmed framework will apply across different metals and conditions. Do these findings generalize to other systems, or are they peculiar to specific surface defects and temperatures?
