Hi Georg, if you are trying to refine anisotropic B-factors for a Mn or Mg element only I do not think you need TLS parameters for that. One way to refine specific elements would be in Refinement settings/Modify start model/B-factors/tick "Convert to anisotropic" and select for the Mn or Mg element. Any element that is formatted as anisotropic will remain so through subsequent rounds of refinement. All the best,John On Wednesday, September 10, 2025 at 01:18:06 AM CDT, Georg Mlynek wrote: Dear scientific community, I ticked TLS parameters in Strategy and in Selection Editor I choose 1 group/chain. Then under Anisotropy elements I typed: element Mn or element Mg Running this throws the error: Bad (empty or mixed) selection in adp_individual_iso. What would be the right input under Isotropic atoms so the TLS is not mixed up. Many thanks, br Georg. _______________________________________________ phenixbb mailing list -- [email protected] To unsubscribe send an email to [email protected] Unsubscribe: phenixbb-leave@%(host_name)s