Scientists Find a Hidden State Inside Liquid Metal That Shouldn’t Exist

Motionless atoms can trap liquid metal in a strange new state that shouldn’t exist.

Scientists have discovered that a liquid does not always behave the way it seems. Even when a material is fully molten, some of its atoms can remain fixed in place, no matter how hot it gets. These stationary atoms strongly influence how a liquid turns into a solid and can even give rise to an unusual state of matter known as a corralled supercooled liquid.

Why Solidification Matters

The process of solid formation underpins many natural phenomena, including mineralization, ice growth, and the folding of protein fibrils. It is also critical for a wide range of technologies. Pharmaceuticals rely on controlled solidification, as do metal-based industries such as aviation, construction, and electronics.

Watching Metal Freeze at the Atomic Scale

To investigate how liquids solidify, researchers from the University of Nottingham and the University of Ulm in Germany used transmission electron microscopy to observe molten metal nano droplets as they cooled. Their results were published in ACS Nano.

Professor Andrei Khlobystov, who led the research, said, “When we consider matter, we typically think of three states: gas, liquid, and solid. While the behavior of atoms in gases and solids is easier to understand and describe, liquids remain more mysterious.”

Theoretical modeling explores the movement of atoms within a liquid nanodroplet of platinum confined inside a defect in a carbon support. The colors represent the mobility of the atoms: platinum atoms at the edges are much less mobile and create an atomic corral around the more mobile atoms located in the center. Credit: University of Nottingham

The Chaotic Motion of Liquid Atoms

Atoms inside a liquid move in a highly complex way, much like people pushing through a crowded space. They rush past one another while continuing to interact. Capturing this behavior is especially difficult during the moment when a liquid begins to freeze, even though this transition determines the final structure of the material and many of its practical properties.

Melting Nanoparticles on Graphene

Dr. Christopher Leist, who carried out the transmission electron microscopy experiments at Ulm using the low voltage SALVE instrument, said, “We began by melting metal nanoparticles, such as platinum, gold, and palladium, deposited on an atomically thin support—graphene. We used graphene as a sort of hob for this process to heat the particles, and as they melted, their atoms began to move rapidly, as expected. However, to our surprise, we found that some atoms remained stationary.”

Further investigation revealed that these immobile atoms were tightly bound to the support at specific defect sites. This strong attachment held even at extremely high temperatures. By focusing the electron beam, the researchers could create more defects and directly control how many atoms stayed pinned within the liquid.

Electron Beams and a New Phase of Matter

Professor Ute Kaiser, who established the SALVE center at Ulm University, said, “Our experiments have surprised us as we directly observe the wave-particle duality of electrons in the electron beam. We visualize the material using electrons as waves. At the same time, electrons behave like particles, delivering discrete bursts of momentum that can either move or, surprisingly, even fix atoms at the edge of a liquid metal. This remarkable observation has allowed us to discover a new phase of matter.”

The team has previously used the same approach to record films of chemical reactions involving individual molecules, including the first time a chemical bond was seen breaking and reforming in real time. This technique allows scientists to observe chemistry one atom at a time.

How Stationary Atoms Change Freezing

In the new experiments, the researchers found that pinned atoms dramatically alter the way a liquid solidifies. When only a few atoms are stationary, crystals grow normally from the liquid until the entire particle becomes solid. When many atoms are fixed in place, however, this orderly process breaks down, and crystal formation is completely blocked.

Professor Andrei Khlobystov from the University of Nottingham said, “The effect is particularly striking when stationary atoms create a ring that surrounds the liquid. Once the liquid is trapped in this atomic corral, it can remain in a liquid state even at temperatures significantly below its freezing point, which for platinum can be as low as 350 degrees Celsius—that is more than 1,000 degrees below what is typically expected.”

From Supercooled Liquid to Unstable Solid

When the temperature drops far enough, the trapped liquid eventually becomes solid. Instead of forming a crystal, it turns into an amorphous metal with no regular atomic pattern. This form is extremely unstable and exists only because the stationary atoms hold it in place. If that confinement is disturbed, the built-up tension is released, and the metal quickly rearranges into its normal crystalline structure.

Implications for Catalysts and Materials Science

Dr. Jesum Alves Fernandes, a catalysis expert at the University of Nottingham, said, “The discovery of a new hybrid state of metal is significant. Since platinum on carbon is one of the most widely used catalysts globally, finding a confined liquid state with non-classical phase behaviour could change our understanding of how catalysts work. This advancement may lead to the design of self-cleaning catalysts with improved activity and longevity.”

Toward Atomically Corralled Matter

Until now, nanoscale corralling had only been demonstrated for photons and electrons. This study marks the first time atoms themselves have been corralled. Professor Andrei Khlobystov said, “Our achievement may herald a new form of matter combining characteristics of solids and liquids in the same material.”

Looking ahead, the researchers aim to precisely control the placement of pinned atoms to build larger and more complex corrals. Such advances could enable more efficient use of rare metals in clean technologies, including energy conversion and storage.

Reference: “Stationary Atoms in Liquid Metals and Their Role in Solidification Mechanisms” by Christopher Leist, Sadegh Ghaderzadeh, Emerson C. Kohlrausch, Johannes Biskupek, Luke T. Norman, Ilya Popov, Jesum Alves Fernandes, Ute Kaiser, Elena Besley and Andrei N. Khlobystov, 9 December 2025, ACS Nano.
DOI: 10.1021/acsnano.5c08201

This work is funded by the EPSRC Programme Grant ‘Metal atoms on surfaces and interfaces (MASI) for sustainable future.’

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