An international team of researchers from the University of Nottingham and the University of Ulm has found that in molten metal, some atoms can remain completely motionless even at temperatures hundreds of degrees above the melting point. These fixed atoms form an entirely new state of matter, a supercooled liquid trapped between liquid and solid. The study was published in ACS Nano.

How Atoms Become Trapped in a Liquid

Classical physics says that in a liquid, atoms move chaotically and constantly exchange places. However, experiments with nanoparticles of platinum, gold, and palladium on ultrathin graphene revealed a different behavior. When heated to their melting point, most atoms behaved as expected, but some became firmly attached to point defects in the substrate and did not move at all.

Using the SALVE transmission electron microscope, the researchers observed individual atoms in real time. By controlling the concentration of defects with the electron beam, they could adjust the proportion of immobile atoms. The outcome was unexpected: when enough atoms remained fixed, crystallization of the metal was completely blocked, and the liquid stayed liquid even at temperatures hundreds of degrees below its freezing point.

A New State Between Liquid and Solid

The researchers referred to this as a hybrid state, a trapped supercooled liquid. Previously, similar effects could be created only for photons and electrons, but this is the first time it has been demonstrated for atoms of matter.

The discovery helps explain unusual behavior in catalysts, such as platinum on carbon, one of the most widely used systems in the world. According to the researchers, the presence of immobile atoms may account for previously unknown self-cleaning and durability properties in such materials.

Outlook: From Catalysts to Clean Energy

In the future, the team plans to create more complex and extended atomic traps. This could make it possible to:

• reduce the consumption of rare metals such as platinum and palladium
• develop new catalysts for fuel cells
• design materials for energy storage and conversion

Summary

Physicists have for the first time caused some atoms in a liquid metal to remain motionless, creating a new hybrid state, a trapped supercooled liquid. The discovery explains catalyst behavior and opens paths to saving rare metals and developing materials for clean energy. It serves as additional evidence that at the nanoscale, familiar phase transitions work very differently.