Hi Jan,
in the final stages of refining a structure, I would like to optimize the restraint weights for geometry and B factors.
Good idea! Although phenix.refine computes "optimal" weight automatically, the values vary from structure to structure.
It seems to work fine for geometry by defining "refinement.target_weights.wxc_scale=1.0".
Yes, I would try an array of values 0.25, 0.5, 1.0, 1.5, 2.0, 2.5.
However, when the respective definition for B-factors does not seem to have an impact at all.
This is very weird. We exercise this in out tests regularly, so it changing wxu_scale should have an impact. It may be that values range for you structure is somehow different... Can you try the extreme values: very big (wxu_scale=10) and very small (wxu_scale=0.1) and see if this makes a difference? Are you using TLS (if yes, then this behavior is explainable)?
The main reason why I try to fiddle around with the B-weights is that coot gives me a whole bunch of red bars in the Temperature factor variance analysis...
The variability of ADP depends on many factors: resolution, model used for global motion (TLS), how internal degrees of freedom modeled ... I do not know if Coot analysis takes this all into account. Otherwise I would use the "red bars" analysis with some care. Pavel.