Hi all,<br><br>  I have a sulfate ion sitting on a 2-fold axis of symmetry.  If I set all the atom occupancies to 0.5 and refine using phenix.refine (Phenix v. 1.5-2) the occupancies are changed to 0.00 for the sulfur, 1.00 for three of the oxygen&#39;s, and 0.72 for the fourth oxygen.  Can anyone explain this?<br>
<br>Thanks in advance,<br>Jon<br>