Scuola AIC 2023 – Webinar Landing Page

ELECTRON
CRYSTALLOGRAPHY
A deep dive into nanocrystals

AIC2023 International School

The interest in electron diffraction (ED) has significantly increased in the last ten years in parallel with the automation of routines for data collection, usually performed with a transmission electron microscope (TEM). The long-standing issue of multi-scattering (dynamical effects) typical of in-zone oriented patterns was significantly mitigated by the possibility to perform three-dimensional, single-crystal-like data acquisitions. This protocol, generally referred as three-dimensional electron diffraction (3DED) or microcrystal electron diffraction (MicroED), allows for the acquisition of structural data from single crystals with size of few microns to few tens of nanometers, regardless of the nearby presence of other phases. Therefore, 3DED was successful for the structure determination of a number of inorganic and organic new compounds that were previously considered intractable by X-ray diffraction methods. Moreover, ED is more sensitive to light atoms, ionic charges and the absolute structure in chiral compounds. Such potential can be fully exploited through a careful structural refinement that considers the residual dynamical effects. Dedicated single-crystal electron diffractometers have recently appeared on the market, testifying the growing interest in 3DED. However, the automation of TEM interfaces brought also other interesting developments, like the possibility to perform serial-ED data collections on extremely beam sensitive materials, with a procedure similar to a typical X-ray Free Electron Laser (XFEL) acquisition, and the possibility to perform phase-orientation mapping with a resolution approaching the nanometer.

The AIC2023 School will focus on the currently available procedures for 3DED analysis.

Students will be first introduced to the peculiarities of ED and then driven through data acquisition procedures and data reduction software. The school will cover both well-established 3DED protocols, based on step-wise acquisition and beam-precession, and more recent protocols based on continuous data acquisition through latest fast and sensitive detectors, particularly suitable for organics and macromolecules. Methods and routines for structure solution and refinement will be described, with a special focus on the treatment and use of residual dynamical effects. Specific features and issues related with inorganic, small-molecule organics and macromolecular compounds will be stressed. All these topics will be covered in frontal lectures and practical activities that will allow students to use first-hand several softwares for 3DED data reduction, structure solution and structure refinement. Students will also participate to lab activities, including 3DED data acquisition and advanced sample preparation for ED experiments. The last part of the school will finally introduce other cutting-edge methodologies, like serial-ED, phase-orientation mapping and electron pair-distribution function (ePDF).

At the end of the school, students are expected to have acquired a comprehensive understanding of advantages and limits of ED methods and to be able to perform 3DED data reduction by themselves on their own samples of interest. For most students, the AIC2023 School will also be the starting point for establishing connections in the growing field of electron crystallography.