Just a comment: typically the A and B atoms cluster with a given NN distribution function to help set the
structure. In our experience the results from FEFF are often not very sensitive to the distribution but you
can try a couple of sample distributions to check this.\
  
John



On Tue, Apr 28, 2020 at 9:29 AM Matt Newville <newville@cars.uchicago.edu> wrote:
Hi Dien,

Yes, basically Artemis / Atoms cannot handle partial occupancy for crystallographic sites because partial occupancy is not readily translated to a cluster of atoms.  So, what you have to do is start with a CIF without fractional occupancy, say that has only Ca or only U in that site, and generate a cluster of atoms from it.  Then, you can (and here, have to) edit that cluster of atoms to replace some of the Ca/U with U/Ca.  Which ones, and how many, is up to you.  

--Matt




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