I have 2 Zn ions which are defined as HETATM, in my structure. I am using tls and bgroup refinement for the whole structure. It seems like the Zn ions are treated as one group. They always have the same B-value. I would like to refine the B-value of the ZN ions separately, but refine the rest of the structure with bgroup refinement. Is that possible? How would I do this? Ursula -- Ursula Schulze-Gahmen, Ph.D. Project Scientist UC Berkeley, QB3 360 Stanley Hall #3220 Berkeley, CA 94720-3220 (510) 643 9491