Atomic Structure Determination of Nanocrystals Using Precession Electron Diffraction Tomography (PEDT)

Why Nanocrystal Structure Determination Remains Challenging

Nanocrystalline materials are commonly used in geology, pharmaceuticals, and materials science. However, solving their atomic structures remains challenging. While traditional X-ray diffraction (XRD) techniques require crystals few microns in size, especially when embedded in complex matrices, TEM-based electron diffraction techniques (micro-ED) are affected by strong dynamical scattering. This distorts diffraction intensities and limits the accuracy of structural refinement — particularly in beam-sensitive samples. A successful approach must reduce the dynamical scattering effects, maximize data quality, and track the sample reliably during tilt series acquisition — all with minimal electron dose.

PEDT Workflow with Tescan TENSOR

A natrolite sample was prepared by dispersing fine powder in isopropanol and drop-casting onto a holey carbon grid. After plasma cleaning, a single ~2 µm crystal was selected for analysis.

Using Tescan TENSOR, electron diffraction tilt series were acquired through stepwise 4D-STEM mapping combined with electron beam precession at a semi-angle of 0.5°. The sample was tilted in 1° increments, and at each position a 19 × 16 tile map was recorded.

Only high-quality diffraction tiles were selected and averaged. Tescan’s XYZ reference tracker ensured beam centering and minimized exposure. The hybrid-pixel detector captured patterns at fast readout speed with low background and high contrast.

This approach avoided contamination, minimized background from the support film, and distributed the electron dose evenly across the sample — preserving sensitive regions while collecting sufficient data for analysis.

High-Quality Diffraction for Confident Structural Refinement

The acquired dataset was processed using PETS2 software. Lattice parameters and crystal symmetry were determined, followed by structure solution and refinement.

The final data showed:

• High resolution better than 0.63 Å
• 73% completeness across the tilt range
• Observed R-factor below 8%

These results enabled confident localization of all non-hydrogen atoms. Difference maps also revealed hydrogen atom positions, which are typically inaccessible via XRD.

This study demonstrates that PEDT with Tescan TENSOR is highly effective for atomic structure determination and analysis of nanocrystals, even when crystals are small, beam-sensitive, or part of complex mixtures.