> I have another situation. i.e. three atoms at two equivalent sites > in La( Mg0.5Sn0.25Ti0.25)O3.
This is really not complicated. All you can expect is to be able to refine the average scattering power of each site. To do that you could fix an arbitrary scattering power and refine the site occupation number; their product is then the site scattering power. Then write down any relations you have between the average scattering powers of the sites, the numbers of different atoms (stoichiometry) and their individual scattering powers, and you may or may not have enough information to obtain the occupancy of each site by each kind of atom. Don't just rely on refining parameters without understanding what they mean. _____________________________________________________________ Dr Alan Hewat, ILL Grenoble, FRANCE <[EMAIL PROTECTED]>fax+33.476.20.76.48 +33.476.20.72.13 (.26 Mme Guillermet) http://www.ill.fr/dif/people/hewat/ _____________________________________________________________
