[phenixbb] coordinate refinement and maps

Hi all, I am refining a protein with metal-ligand complexes. Is it possible to refine only y coordinates for an atom (on two fold) while keeping X and Z fixed using Phenix? Also is there a way to calculate something like anomalous difference-difference map (Anomalous Fobs - Anomalous Fcalc) to identify any additional atoms bound at metal sites. Thanks in advance for the help! Subhani