This article describes the application of CrysAlisPro software tools in handling data sets of non-Merohedral crystals. By using the software tools of CrysAlisPro, it is relatively easy to obtain high-quality structures.
The document describes the challenges associated with collecting diffraction data from crystals exhibiting non-merohedral twinning, where a low percentage fit of indexed reflections often indicates the presence of a secondary lattice. It details an example case collected at the Indian Institute of Technology, Mumbai, using an Xcalibur S system.
Some institutions have a policy not to collect data on any crystal with a fit lower than around 70%.
More than 90% of the 30,000 reflections are considered to be overlapped with a reflection from the second lattice.
In this case 82% of the total reflections fit two identical unit cells.
The R value drops to 5.9% on application of an analytical absorption correction.