[phenixbb] How to assign Half occupancy to metal ion in protein crystal

Dear all, I am refining the protein structure and i want add metal ion in the structure, the site is present in between protein chain and its symmetry mate. when i added metal and refined, it was showing the high B factor and symmetry related metal on the same site. i want to assign the occupancy half and refine but in coot i am unable to do. Is there any method to do this. Thanks in Advance -- Sharan C/O Dr. J V Pratap Senior Research Fellow, CSIR-Central Drug Research Institute, Lucknow