Complex Organic – Synchrotron Data
Files needed: luca_7-oabicycle_50k.xye, oxa50.cif, oxa50.inp
Learning outcomes: This tutorial shows how one can refine a complex organic sample with 3 molecules in the asymmetric unit using rigid bodies in a z-matrix formalism. This allows you to force all molecules to be equivalent and to have additional non-crystallographic internal symmetry.
1. Save the files above in your working directory.
2. Go through the menu for a “Simple Rietveld Refinement”. For the instrument select “synchrotron”. The wavelength was 0.85025 Angstroms. Use 90 for the LP Factor. Fit the data from 3.8 to 50 degrees. Refine a single overall temperature factor. Introduce a 4th order spherical harmonic for preferred orientation. You should be able to get Rwp=8.5% or below. If the default peak shape parameters don’t work try adding lh 0.5 at the end of the la 1 lo 0.85024 line.
3. Open the file oxa50.inp. This describes the refinement using rigid bodies in all their gory details!