Hi Andrew,

My question is what is the best method for generating the correct distribution of atoms at these points. Naively, one would just randomly select 30% of the shared points to be aluminums and set the other 70% as silicon. I doubt that this is ideal.

Short answer: there is nothing in the cctbx that would help you directly. I have a past as a zeolite person. My understanding was that the 30%/70% occupancy factors are a way to model spatial averages, as that's all you get from the diffraction experiment. How to handle the overlapping atoms depends highly on the context. E.g. in refinement I'd keep the overlapping atoms but constrain the coordinates to be identical. For graphical presentation I'd probably want to find a nice way to present the mixed occupancy, i.e. I wouldn't want to simply draw two crosses on top of each other. What is your context? Cheers, Ralf ____________________________________________________________________________________ Never Miss an Email Stay connected with Yahoo! Mail on your mobile. Get started! http://mobile.yahoo.com/services?promote=mail