Measuring Dominant Local Structures in Amorphous Materials Using Nanobeam Electron Diffraction*

The atomic structure of amorphous materials has long been a mystery. Due to the lack of long-range periodical order, traditional techniques such as X-ray diffraction cannot be used to directly measure atomic coordinates. Through the analysis of pair-distribution functions, measurements of averaged structural features such as average bond lengths can be determined. By combining experimental data with simulations such as in reverse Monte-Carlo simulations, some models of 3D atomic structures can be determined. However it has not yet been possible to determine any local structure directly from experiment.
In this work, a type of image processing commonly applied in single particle cryo-electron microscopy is applied to a large set of nanobeam electron diffraction patterns. This produces a set of class-averaged patterns that represent dominant SRO structures within the material. This for the first time allows direct measurements on such structures and may eventually be extended to determine experimental 3D electron density distributions of SRO structure within amorphous materials.