PPubMed14 Apr 2023Cited 27×

Electron crystallography and dedicated electron-diffraction instrumentation Electron crystallography and instrumentation

Petra Simoncic, Eva Romeijn, Eric Hovestreydt, Gunther Steinfeld, Gustavo Santiso-Quiñones, Johannes Merkelbach, S. Parkin

Abstract

Recent years have seen a flurry of research activity in the field of electron diffraction. The introduction of the electron diffractometer, designed to be fully dedicated to its task of providing the best data from electron-diffraction experiments, will be a crucial factor for the continued growth and success of this technology.

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Dedicated electron diffractometers like Eldico ED-1 achieve sub‑10% R1 values for nanocrystal structures, addressing vacuum and dynamical‑scattering challenges.

What’s new

i.Introduction of a fully dedicated electron diffractometer (Eldico ED-1) for 3D electron diffraction
ii.Demonstration of R1 = 9.70% for 1,3,5‑Triphenylbenzene using standard kinematic refinement
iii.Benchmarking of the instrument with four use cases (tyrosine, L‑histidine, D‑histidine, TPB)
iv.Presentation of sample‑preparation strategies for vacuum‑sensitive and beam‑sensitive crystals
v.Discussion of methods to mitigate dynamical scattering through continuous‑rotation data collection

How they did it

Samples were ground, deposited on carbon‑coated Cu grids, and screened by STEM imaging before being centred in a high‑precision goniometer. Continuous‑rotation ϕ‑scans (100‑180°) were recorded on the Eldico ED-1 diffractometer at 160 keV, and data were processed with APEX4, SAINT, SADABS, SHELXD and refined with SHELXL.

What they found

Merged data set completeness = 86.7% with R1 = 14.05% and wR2 = 37.68%
TPB structure refined to R1 = 9.70% (wR2 = 28.05%) using standard kinematic refinement
Resolution achieved down to 0.9 Å for tyrosine and 0.99 Å for TPB

Caveats

✕High vacuum (≤10⁻⁶ bar) can damage hydrated or biological samples
✕Dynamical scattering leads to higher R‑values compared with X‑ray data
✕Continuous rotation often limited to 100‑180° due to instrument geometry
✕Beam‑sensitive crystals may deteriorate during data acquisition

in plain words

Electron diffraction can determine atom positions in crystals that are too small for X‑ray methods. A purpose‑built electron diffractometer keeps the sample in high vacuum and rotates it to collect data, allowing accurate structures even for light elements. This enables analysis of pharmaceuticals and materials that were previously inaccessible.

why it matters

Electron diffraction provides structural information for nanocrystals and light elements that X‑ray diffraction cannot resolve, expanding capabilities in pharmaceuticals and materials science. Dedicated instrumentation improves data quality, making the technique more reliable for real‑world applications.

Follow the thread

electron diffraction electron diffractometer 3D ED dynamical scattering nanocrystallography cryogenic sample preparation

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