The image shows 4D atomic motion captured in an iron-platinum nanoparticle at three different times. (Credit: Alexander Tokarev/Ella Maru Studio)

Adapted from the original release published by UCLA. View the original release.

Everyday transitions from one state of matter to another – such as freezing, melting, or evaporation – start with a process called “nucleation,” in which tiny clusters of atoms or molecules (called “nuclei”) begin to coalesce. Nucleation plays a critical role in circumstances as diverse as the formation of clouds and the onset of neurodegenerative disease.

Scientists have gained a never-before-seen view of nucleation – capturing how the atoms rearrange at 4D atomic resolution (that is, in three dimensions of space and across time). The findings, published in the journal Nature, differ from predictions based on the classical theory of nucleation that has long appeared in textbooks.

The UCLA-led team, which includes collaborators from Berkeley Lab, used a state-of-the-art electron microscope located at the Molecular Foundry. In much the same way a CAT scan generates a 3D X-ray of the human body, atomic electron tomography uses electrons to create stunning 3D images of atoms within a material as the sample is rotated under the microscope.

“Nucleation is basically an unsolved problem in many fields,” said co-author Peter Ercius, a staff scientist at Berkeley Lab’s Molecular Foundry. “Once you can image something, you can start to think about how to control it.”

– Wayne Lewis