Software toolkit aids indexing crystallographic electron diffraction data

Ultrafast electron diffraction (UED) using femtosecond electron pulses is one of the best ways to observe dynamic changes in crystal structure. However, analyzing the resulting diffraction data can be challenging, particularly in indexing the diffraction patterns and identifying the orientation of the crystal lattice. Existing crystallographic tools index patterns using only the positions of the Bragg reflections, which is often insufficient for UED experiments.

Marx and Epp developed a software toolkit, named GARFIELD (Geometry AnalyzeR For sIngle-crystal ultrafast ELectron Diffraction), for a more comprehensive approach to indexing UED diffraction patterns.

Because of the constraints of ultrashort electron pulses, crystal samples used for UED often consist of many crystalline domains with slightly different orientations. This results in the Bragg reflections being blurred and overlapping with other reflections.

While this makes traditional analysis more difficult, the authors’ toolkit uses these less-than-ideal diffraction conditions to employ a least-squares fit to optimize the diffraction parameters.

“We propose to use the reflection intensities in combination with relaxed positional restraints to find potential solutions and to eliminate remaining ambiguities,” said author Alexander Marx.

The software package allows the user to incorporate known information about the crystal, such as the ground state structure, and identify the parameters that best fit the data. The authors believe this will streamline UED experiments.

“Setting up and carrying out single-crystal UED experiments usually takes a considerable amount of time and effort,” said Marx. “Unfortunately, it is not uncommon that the analysis of UED data is significantly delayed or even stopped because of problems with the initial step of indexing. I think our approach can help to overcome this first critical hurdle.”

Source: “GARFIELD, a toolkit for interpreting ultrafast electron diffraction data of imperfect quasi-single crystals,” by Alexander Marx and Sascha Epp, Structural Dynamics (2025). The article can be accessed at https://doi.org/10.1063/4.0000286 .

This paper is part of the Enabling Methods in Ultrafast Electron Diffraction, Scattering and Imaging Collection, learn more here .