[phenixbb] atom selection for elements anisotropic rest TLS

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.