Even the best digital cameras available today typically expose a frame for about 1/4,000 of a second.
But if you want to capture atomic-scale motion, you would need a shutter that fires far more quickly.
In 2023, scientists presented a method that effectively delivers a shutter speed of just a trillionth of a second - roughly 250 million times faster than those digital cameras. That speed is enough to observe a key concept in materials science known as dynamic disorder.
Watch the video below for a summary of what they found:
Put simply, dynamic disorder describes the way groups of atoms can shift and “dance” through a material in particular patterns over a given timescale - set off by something like a vibration or a change in temperature. Researchers still do not fully understand the phenomenon, yet it has a major influence on how materials behave and react.
Why a trillionth-of-a-second shutter matters for dynamic disorder
Having an ultra-fast shutter makes it possible to isolate a much tighter slice of time, which is essential when the subject is moving extremely quickly - such as atoms that are constantly jittering. The same principle applies in everyday photography: use a slow shutter speed to photograph a sporting event and the players will appear blurred.
vsPDF: the “variable shutter atomic pair distribution function” tool
To obtain these extraordinarily rapid snapshots, the new system does not rely on ordinary photographic methods. Instead, it uses neutrons to determine where atoms are. By tracking how neutrons strike and pass through a material, scientists can infer the positions of nearby atoms; changes in the neutrons’ energy levels act like adjustments to shutter speed.
The ability to vary the shutter speed matters just as much as reaching the trillionth-of-a-second mark. It is crucial for separating dynamic disorder from the related but distinct static disorder - the everyday background wobble of atoms in place that does not improve how a material functions.
The researchers call their approach the “variable shutter atomic pair distribution function”, shortened to vsPDF.
"It's only with this new vsPDF tool that we can really see this side of materials," said materials scientist Simon Billinge from Columbia University in New York.
"With this technique, we'll be able to watch a material and see which atoms are in the dance and which are sitting it out."
"It gives us a whole new way to untangle the complexities of what is going on in complex materials, hidden effects that can supercharge their properties," said Billinge.
What vsPDF revealed in germanium telluride (GeTe)
In this study, the team pointed their neutron “camera” at germanium telluride (GeTe) - a material valued for properties that make it widely used to turn waste heat into electricity, or electricity into cooling.
The measurements showed that GeTe, on average, retained a crystal structure at all temperatures. However, at higher temperatures it exhibited stronger dynamic disorder, with atoms converting motion into thermal energy along a gradient that aligns with the direction of the material’s spontaneous electric polarisation.
Understanding these physical structures more clearly sharpens our knowledge of how thermoelectrics function, which in turn supports the development of improved materials and devices - including the power sources used by Mars rovers when sunlight is not available.
What comes next for the vsPDF technique
By building models from what the new camera observes, scientists can refine their understanding of these materials and the processes involved. Even so, there is still substantial work required before vsPDF is ready to become a routine testing method.
"We anticipate that the vsPDF technique described here will become a standard tool for reconciling local and average structures in energy materials," the researchers explained in their paper.
The research was published in Nature Materials.
An earlier version of this article was published in March 2023.
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