Scientists have long sought to better understand the “local structure” of materials, meaning the arrangement and activities of the neighboring particles around each atom. In crystals, which are used in electronics and many other applications, most of the atoms form highly ordered lattice patterns that repeat. But not all atoms conform to the pattern.

When some atoms take up local arrangements that are different than that implied by the overall structure of the crystal, studying the local structure gets more difficult — especially when the atoms are moving. In fact, the inability to clearly see these local effects means researchers are often not aware they can happen.

Now researchers using the Spallation Neutron Source at Oak Ridge National Laboratory have developed a new method of studying the local structure of materials in detail and in real time.

The team developed a variable-shutter pair distribution function, or vsPDF, technique in which neutrons function like a camera but at timescales that are a trillion times faster.

Results of the research, led by Columbia University and scientist Simon Kimber, demonstrate a unique use of neutrons that could become a standard method for reconciling local and overall structures in energy materials. The research also revealed a key mechanism behind the thermoelectric effect, in which temperature differences in a material can be converted into an electric voltage or, conversely, the material can be used to heat or cool when a voltage is applied to it.The new local structure analysis method uses the ultrabright flashes of neutrons produced by SNS. When these neutrons pass through a material, the resulting scattering patterns yield information about the material’s atomic arrangement. Using a novel energy filtering technique, the team determined how to change the effective shutter speed of the energy to produce representations — or images — of the atomic arrangement. In conventional cameras, images of moving objects blur at slower shutter speeds. Gradually increasing the shutter speed will eventually freeze the moving atoms in an unblurred image.