Content:
When working with low-resolution datasets (especially those with very few reflections), some non-default options might be necessary to process the data with autoPROC. It is also often necessary to run some additional steps by hand, ie. taking the initial, autoPROC-generated files as a starting point for more fine-tuning.
Here we will collect some recipes for dealing with such datasets.
The first assumption is, that a dataset can be processed with all defaults, ie. in the same way a high-resolution dataset from the same beamline/instrument and shift would be processed. Of course, this might include some parameter settings defining beam centre convention etc, but nothing specific to a low-resolution dataset.
Even if that run terminates without error, some checks should be done:
If an autoPROC run terminates with an error or some of the above criteria are not met, the following sections will show some possible actions one could take.
A good set of options is to run with
% process -M LowResOrTricky ...
since this will set a few parameters typical for low-res (or any other more challenging) dataset. See output of process -M show what parameters this macro sets.
If the cell and/or spacegroup is known, running with
% process cell="40 50 60 90 90 90" symm=P21212 ...
can help XDS to find the correct indexing solution.
It is also a good idea to restrict the processing to the resolution where there actually are some reflections, eg by giving a resolution limit
% process -R 100.0 3.2 ...
or by specifying the detector edge via
% process autoPROC_XdsKeyword_TRUSTED_REGION="0.0 1.05" ...