ECA lunchtime webinars - Nanocrystalline organic compounds: Crystal structure determination from XRPD and PDF data – What is possible today?

For nanocrystalline organic compounds, crystal structure determination is often challenging. If the X-ray powder diffractogram (XRPD) contains less than about 20-30 sharp peaks, indexing frequently fails, and the lattice parameters remain unknown. Consequently, all classical methods for structure determination from powder data cannot be applied.
If indexing fails, only few methods remain:
1) Recrystallisation attempts trying to obtain better powder data
2) A search for an isostructural compound with a known crystal structure
3) Crystal structure prediction by global lattice-energy minimisations
4) Structure solution by a global fit to the powder pattern without prior knowledge of lattice
parameters and space group ("FIDEL Global Fit")
5) Structure determination by a fit to the pair-distribution function ("Global PDF fit")
6) Electron diffraction

This presentation focusses on the FIDEL Global fit and on the Global PDF fit.