Seminar Date: Tuesday, February 25, 2025
Time: 11:00 AM PT
Location: 67-3111 & Zoom
Talk Title: Reuniting Crystallography with Real Space: Ab Initio Structure Elucidation with 4D-STEM
Zoom link
Abstract:
Structure elucidation via crystallographic methods has historically lacked experimental access to real-space information, instead relying exclusively on diffraction-space measurements of Bragg reflections. Here we exploit the dual-space imaging power of 4D scanning transmission electron microscopy (4D-STEM) to logically integrate real-space information into the crystallographic workflow. We demonstrate that virtual apertures assembled by watershed segmentation of high-angle annular dark-field images enable (i) pixel-by-pixel extraction of coherent Bragg signal from clusters of closely spaced nanocrystals and (ii) retroactive reduction of unwanted multiple scattering artifacts such as Kikuchi lines. This strategy empowers us to simply pick and choose whichever regions of interest generate the highest-quality diffraction patterns, allowing us to solve eight independent structures of the metal-organic framework UiO-66 from specimens whose agglomerated morphology proved intractable for conventional microcrystal electron diffraction (microED). Our approach divulges the first 4D-STEM structures determined by ab initio phasing at subangstrom resolution.
