Hi Pawel,

Dear all,

Instruction says: Anomalous groups refines the anomalous coefficients f' and f'' for anomalously scattering atoms such as Se or heavy metals; it is only appropriate if you have anomalous data (I+/I- or F+/F-).

How do I indicate which atoms to be considered?

you should know which atoms were anomalous scatterers from your diffraction experiment..

Then you can select atoms for which you want to refine f' and f'' as explained here (command line):
http://www.phenix-online.org/documentation/refinement.htm#anch130
or whatever the GUI setup for this is.

Pavel