vsPDF is a neutron‑based method that acts like a trillionth‑of‑a‑second shutter to reveal dynamic disorder — short‑lived, correlated atomic motions in solids. Applied to germanium telluride (GeTe), the technique shows increasing temperature‑driven atomic exchanges aligned with the material’s spontaneous polarization. By separating dynamic from static disorder, vsPDF can improve models for thermoelectric materials and may help design better energy devices; the results appear in Nature Materials.
Trillionth‑of‑a‑Second Neutron “Shutter” Reveals Atomic ‘Dance’ in Thermoelectric Material
vsPDF is a neutron‑based method that acts like a trillionth‑of‑a‑second shutter to reveal dynamic disorder — short‑lived, correlated atomic motions in solids. Applied to germanium telluride (GeTe), the technique shows increasing temperature‑driven atomic exchanges aligned with the material’s spontaneous polarization. By separating dynamic from static disorder, vsPDF can improve models for thermoelectric materials and may help design better energy devices; the results appear in Nature Materials.
13:25, 02.11.2025Science
Trillionth‑of‑a‑Second Neutron “Shutter” Reveals Atomic ‘Dance’
Typical consumer cameras expose their sensors for about one four‑thousandth of a second. Observing atomic motion requires a shutter many orders of magnitude faster. In 2023, researchers introduced a technique that effectively creates a trillionth‑of‑a‑second time window — roughly 250 million times faster than those consumer cameras — allowing direct observation of a phenomenon called dynamic disorder in solids.
What is dynamic disorder?
Dynamic disorder refers to groups of atoms moving, swapping positions or oscillating together over short time windows, often triggered by vibrations or temperature changes. These correlated motions influence a material’s properties and performance but are difficult to separate from static displacements using conventional methods.
How vsPDF works
The new method, called variable‑shutter atomic pair distribution function (vsPDF), uses neutrons rather than light to probe atomic positions. When neutrons scatter from a sample, detectors record their energies and trajectories. By selecting different energy windows — effectively changing the instrument’s temporal resolution — researchers create variable “shutter” intervals that isolate motions on distinct timescales. Combining this with the atomic pair distribution function (PDF) analysis reveals how local atomic correlations evolve over those time windows.
“It's only with this new vsPDF tool that we can really see this side of materials,” said materials scientist Simon Billinge of Columbia University. “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.”
Demonstration on germanium telluride (GeTe)
The team applied vsPDF to germanium telluride (GeTe), a material widely studied for thermoelectric and electrocaloric applications — it can convert waste heat into electricity or, conversely, electricity into cooling. The measurements showed that, on average, GeTe retains a crystalline structure across the studied temperature range. However, at higher temperatures the material displays increased dynamic disorder: atoms exchange motion into thermal energy along a gradient that aligns with the material’s spontaneous electric polarization.
Why this matters
Separating dynamic from static disorder reveals hidden, time‑dependent atomic mechanisms that can strongly affect transport, polarization and energy conversion. Better models informed by vsPDF data can guide the design of improved thermoelectric materials and devices — from waste‑heat harvesters to instruments used on planetary missions when sunlight is unavailable.
The researchers note that further development and broader adoption are still needed before vsPDF becomes a routine characterization tool, but they expect it to become a standard approach for reconciling local and average structures in energy materials. The study was published in Nature Materials.
Quick analogy
Think of taking a picture of a fast sports play: a slow shutter blurs the players, while a very fast shutter freezes individual positions. vsPDF gives materials scientists time‑resolved “snapshots” of atomic motion so they can tell who’s moving and who’s not.