[phenixbb] Phenix real space refine use for Cryo-EM model refinement

Hi, I am using Phenix real space refine to refine my cryo-EM model. My model is looking good (based on molprobity statistics) but I would like to run an additional round of Phenix refinement without allowing the program to move the side chains. From what I see, Phenix moves the side chains by default. What settings can I use to avoid this? Thank you.