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Tips and Tricks: Difference between revisions
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The advantage of doing this is that one may easily calculate an anomalous difference Fourier map (this can e.g. be performed in [coot]) to identify ions in the structure. For example, a Mn ion (f"=1.35 at 1 A°) may easily be distinguished from a Mg ion (f"=0.076 at 1 A°). Calibration of the anomalous peak height can be done using the sulfur atoms (f"=0.24 at 1 A°), and the tables of anomalous scattering coefficients at http://skuld.bmsc.washington.edu/scatter/AS_periodic.html. | The advantage of doing this is that one may easily calculate an anomalous difference Fourier map (this can e.g. be performed in [coot]) to identify ions in the structure. For example, a Mn ion (f"=1.35 at 1 A°) may easily be distinguished from a Mg ion (f"=0.076 at 1 A°). Calibration of the anomalous peak height can be done using the sulfur atoms (f"=0.24 at 1 A°), and the tables of anomalous scattering coefficients at http://skuld.bmsc.washington.edu/scatter/AS_periodic.html. | ||
== Index and integrate multiple-crystal diffraction == | |||
It can happen that you have two different mono-crystals in your loop, and that both are in the X-ray trajectory. If their relative orientation is sufficiently distinct, it is easy with XDS to index and integrate both crystal diffraction from the same data-set. You end-up with two distinct reflection files and can try to scale them using XSCALE to complete or increase the redundancy of your measurement. | |||
After indexation and integration of a first lattice, you can remove the un-indexed reflections to create a new SPOT.XDS file (don't forget to copy the result of the first processing!) and re-run XDS from the IDXREF stage : | |||
mkdir xtal1 | |||
cp *.* xtal1 | |||
cp SPOT.XDS SPOT.XDS.1 | |||
grep " 0 0 0" SPOT.XDS.1 > SPOT.XDS | |||
echo " JOB= IDXREF INTEGRATE CORRECT" >> XDS.INP | |||
xds_par | |||