New 'camera' with shutter speed oftrillionth of a second sees through
dynamic disorder of atoms

Date:
March 7, 2023
Source:
Columbia University School of Engineering and Applied Science
Summary:
Researchers have developed a new 'camera' that sees the local
disorder in materials. Its key feature is a variable shutter speed:
because the disordered atomic clusters are moving, when the team
used a slow shutter, the dynamic disorder blurred out, but when they
used a fast shutter, they could see it. The method uses neutrons
to measure atomic positions with a shutter speed of around one
picosecond, a trillion times faster than normal camera shutters.


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FULL STORY ========================================================================== Researchers have developed a new "camera" that sees the local disorder
in materials. Its key feature is a variable shutter speed: because the disordered atomic clusters are moving, when the team used a slow shutter,
the dynamic disorder blurred out, but when they used a fast shutter,
they could see it. The method uses neutrons to measure atomic positions
with a shutter speed of around one picosecond, a trillion times faster
than normal camera shutters.


========================================================================== Researchers are coming to understand that the best performing materials
in sustainable energy applications, such as converting sunlight or waste
heat to electricity, often use collective fluctuations of clusters of
atoms within a much larger structure. This process is often referred to as "dynamic disorder." Dynamic disorder Understanding dynamic disorder in materials could lead to more energy-efficient thermoelectric devices, such
as solid-state refrigerators and heat pumps, and also to better recovery
of useful energy from waste heat, such as car exhausts and power station exhausts, by converting it directly to electricity. A thermoelectric
device was able to take heat from radioactive plutonium and convert it
to electricity to power the Mars Rover when there was not enough sunlight.

When materials function inside an operating device, they can behave as if
they are alive and dancing -- parts of the material respond and change
in amazing and unexpected ways. This dynamic disorder is difficult to
study because the clusters are not only so small and disordered, but
they also fluctuate in time.

In addition, there is "boring" non-fluctuating disorder in materials that researchers aren't interested in because the disorder doesn't improve properties. Until now, it has been impossible to see the relevant dynamic disorder from the background of less relevant static disorder.

New "camera" has incredibly fast shutter speed of around 1 picosecond Researchers at Columbia Engineering and Universite' de Bourgogne
report that they have developed a new kind of "camera" that can see the
local disorder. Its key feature is a variable shutter speed: because
the disordered atomic clusters are moving, when the team used a slow
shutter, the dynamic disorder blurred out, but when they used a fast
shutter, they could see it. The new method, which they call variable
shutter PDF or vsPDF (for atomic pair distribution function), doesn't
work like a conventional camera -- it uses neutrons from a source at
the U.S. Department of Energy'sOak Ridge National Laboratory (ORNL) to
measure atomic positions with a shutter speed of around one picosecond,
or a million million (a trillion) times faster than normal camera
shutters. The study was published February 20, 2023, by Nature Materials.

"It's only with this new vsPDF tool that we can really see this side
of materials," said Simon Billinge, professor of materials science and
applied physics and applied mathematics. "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. 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." New theory on stabilizing local fluctuations
and converting waste heat to electricity The vsPDF tool enabled the
researchers to find atomic symmetries being broken in GeTe, an important material for thermoelectricity that converts waste heat to electricity
(or electricity into cooling). They hadn't previously been able to see the displacements, or to show the dynamic fluctuations and how quickly they fluctuated. As a result of the insights from vsPDF, the team developed a
new theory that shows just how such local fluctuations can form in GeTe
and related materials. Such a mechanistic understanding of the dance will
help researchers to look for new materials with these effects and to apply external forces to influence the effect, leading to even better materials.

Research team Billlinge's co-lead on this work with Simon Kimber,
who was at the University of Bourgogne in France at the time of
the study. Billinge and Kimber worked with colleagues at ORNL and the
Argonne National Laboratory (ANL), also funded by the DOE. The Inelastic neutron scattering measurements for the vsPDF camera were made at ORNL;
the theory was done at ANL.

Next steps Billinge is now working on making his technique easier to use
for the research community and applying it to other systems with dynamic disorder. At the moment, the technique is not turn-key, but with further development, it should become a much more standard measurement that could
be used on many material systems where atomic dynamics are important,
from watching lithium moving around in battery electrodes to studying
dynamic processes during water- splitting with sunlight.

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========================================================================== Story Source: Materials provided by Columbia_University_School_of_Engineering_and_Applied Science. Original
written by Holly Evarts. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Simon A. J. Kimber, Jiayong Zhang, Charles H. Liang, Gian
G. Guzma'n-
Verri, Peter B. Littlewood, Yongqiang Cheng, Douglas L. Abernathy,
Jessica M. Hudspeth, Zhong-Zhen Luo, Mercouri G. Kanatzidis, Tapan
Chatterji, Anibal J. Ramirez-Cuesta, Simon J. L. Billinge. Dynamic
crystallography reveals spontaneous anisotropy in cubic GeTe. Nature
Materials, 2023; 22 (3): 311 DOI: 10.1038/s41563-023-01483-7 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/03/230307174315.htm

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