Success of SHELXD substructure solution. (a) SHELXD correlation coefficient for all reflections (CCall) versus weak reflections (CCweak) as a function of k. Sets of trial solutions are shown for multiple values of k and are coloured by the best combined figure of merit (CFOM) from that set of trials from blue to red. Note the maximum at k = 0.97789. (b) Post facto comparison of the best substructures from (a) against known substructures. Known substructures are computed by peak-searching a model-phased RIP difference map. The position and relative intensity of the resultant substructure sites are plotted in the xy plane of the unit cell. More intense sites (i.e. sites with the most radiation damage such as the Sγ atoms of some cysteines) are shown as larger circles. This reference substructure is then used to evaluate trial solutions from SHELXD. If a particular site is present in the SHELXD solution the circle is coloured blue, otherwise it is coloured grey. Note that the proportion of found (blue) sites is maximal at at k = 0.97789, like the best CFOMs.