Polymorphism is very important in the pharmaceutical industry where it also occurs very frequently in other organic materials like pigments and proteins. Physical properties of organic compounds (specially for drug design) depend on their precise crystal structure. 3D electron diffraction tomography sheds light to the crystal structure of organic compounds and proteins.


Structural Characterization in TEM by 3D Electron Diffraction / Micro-ED

Dr. Partha Das Application Scientist NanoMEGAS Belgium


In recent  years  there has been a huge interest in characterization for various materials where more than 300 structures have been solved (minerals, zeolites, MOFS, aperiodic crystals, archaeological  artefacts, functional materials, organic pharmaceuticals, proteins etc.) using 3D Electron Diffraction from nanometer size crystals in TEM. The principle of acquiring TEM 3D-ED data consists of focusing the electron beam on a nanometer size crystal (50-500 nm), while sampling thereciprocal/diffraction space in small steps using beam precession or continuous  crystal rotation (with or without beam PED,  technique known as 3D Electron Diffraction Tomography/Micro-ED). ED intensities can be registered using CCD cameras or ultra- sensitive pixelated detectors. Acquired 3D-ED data can be used to determine ab-initio  crystal unit cell, space group and atomic positions. Further dynamical refinement can also be performed using PED to detect H atoms, refine occupancies  an  improve  reliability of the structural model down to 1-3 pm accuracy.  In this webinar various examples will be shown how 3D-ED method has been applied successfully to solve structures of a big variety  of  nanocrystalline materials.



Schmidt, M. U., et al. “Electron Diffraction, X-Ray Powder Diffraction and Pair-Distribution- Function Analyses to Determine the Crystal Structures of Pigment Yellow 213, C23H21N5O9.” Acta Crystallographica Section B: Structural Science, vol. 65, no. 2, 2009, pp. 189–99, doi:10.1107/S0108768109003759.


Lanza, A., et al. “Nanobeam Precession-Assisted 3D Electron Diffraction Reveals a New Polymorph of Hen Egg-White Lysozyme.” IUCrJ, vol. 6, International Union of Crystallography, 2019, pp. 178–88, doi:10.1107/S2052252518017657.


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