Dear Phenix developers, I am rigid-body refining a PM-twinned structure (C2221 => P6x22) with the operators suggested from xtriage or SFcheck but I keep running into this same error (version 1.4.3 or latest cci aps bundles); 1/2*h-1/2*k,-3/2*h-1/2*k,-l 1/2*h+1/2*k,3/2*h-1/2*k,-l Any suggestions as to how I can resolve this? Many thanks in advance, Jonathan Elegheert PhD student Ghent University Belgium ------------------------------------------------------------------------- Traceback (most recent call last): File "/usr/local/cciapps/cci_apps_sources/phenix/phenix/command_line/refine.py", line 16, in <module> command_line.run(command_name="phenix.refine", args=sys.argv[1:]) File "/usr/local/cciapps/cci_apps_sources/phenix/phenix/refinement/command_line.py", line 89, in run call_back_after_monitor_collect=call_back_after_monitor_collect) File "/usr/local/cciapps/cci_apps_sources/phenix/phenix/refinement/driver.py", line 1121, in run call_back_after_monitor_collect = call_back_after_monitor_collect) File "/usr/local/cciapps/cci_apps_sources/phenix/phenix/refinement/strategies.py", line 190, in refinement_machine twin_law = sgtbx.rt_mx( params.twinning.twin_law ) RuntimeError: cctbx InternalError: /net/garter/scratch1/rwgk/auto_build/sources/cctbx/sgtbx/rt_mx.cpp(230): Unsuitable value for rational rotation matrix.