Round robin on structure analysis from 3D electron diffraction data

Area of Science:

• Crystallography
• Materials Science
• Electron Microscopy

Background:

• Three-dimensional electron diffraction (3D ED) has advanced significantly.
• The technique's accuracy and reproducibility across different laboratories remain untested.

Purpose of the Study:

• To assess the accuracy and reproducibility of 3D ED.
• To evaluate 3D ED performance on diverse sample types (inorganic and organic) across multiple institutions.

Main Methods:

• A round-robin experiment involving seven laboratories using 3D ED.
• Testing on two inorganic and one organic test structure.
• Utilizing various transmission electron microscopes, acceleration voltages, methodologies, and detectors.

Main Results:

• 3D ED demonstrated remarkable accuracy, with atomic position errors around 0.05 Å for inorganic and 0.15 Å for organic samples (kinematical refinement).
• Dynamical refinement further enhanced accuracy, reducing R factors and improving structural models.
• Hydrogen atom positions and absolute structure determination were achieved for both sample types.

Conclusions:

• 3D ED is a highly accurate and reproducible technique for crystal structure determination.
• Dynamical refinement is a robust method for improving accuracy and obtaining detailed structural information.
• The study validates 3D ED for analyzing both inorganic and beam-sensitive organic materials.