Hello, Sorry for reposting, I am trying to get a better response with a more detailed subject line. I am seeing an internal error while trying to conduct joint x-ray/neutron refinement, and any help with the issue below would be greatly appreciated. Thank you very much in advance: ================================ ADP refinement=============================== Traceback (most recent call last): File "/sware/phenix-1.6.4-486/linux64/phenix-1.6.4-486/phenix/phenix/command_line/refine.py", line 11, in <module> command_line.run(command_name="phenix.refine", args=sys.argv[1:]) File "/sware/phenix-1.6.4-486/linux64/phenix-1.6.4-486/phenix/phenix/refinement/command_line.py", line 89, in run call_back_handler=call_back_handler) File "/sware/phenix-1.6.4-486/linux64/phenix-1.6.4-486/phenix/phenix/refinement/driver.py", line 1182, in run call_back_handler = call_back_handler) File "/sware/phenix-1.6.4-486/linux64/phenix-1.6.4-486/phenix/phenix/refinement/strategies.py", line 735, in refinement_machine h_params = h_params) File "/sware/phenix-1.6.4-486/linux64/phenix-1.6.4-486/cctbx_project/mmtbx/refinement/adp_refinement.py", line 192, in __init__ all_params = all_params) File "/sware/phenix-1.6.4-486/linux64/phenix-1.6.4-486/cctbx_project/mmtbx/refinement/adp_refinement.py", line 216, in refine_adp model.set_refine_individual_adp() File "/sware/phenix-1.6.4-486/linux64/phenix-1.6.4-486/cctbx_project/mmtbx/model.py", line 1035, in set_refine_individual_adp iselection = selection_iso.iselection()) RuntimeError: cctbx InternalError: /net/anaconda/scratch1/phenix/phenix-1.6.4-486/cctbx_project/cctbx/xray/scatterer_flags.h(417): CCTBX_ASSERT(f.use_u_iso()) failure. This error occurs during the 2nd macro cycle of refinement using this general command: phenix.refine model.pdb data_xray.hkl neutron_data.file_name=data_neutron.hkl input.xray_data.labels=FOBSx input.neutron_data.labels=FOBSn Thanks again. Regards, Louis