In Fullprof such a situation can be handled by a set of linear restraints using CHEMCOMP (see https://www.ill.eu/sites/fullprof/php/Fullprof_News_2002.htm).
However, in my experience such a setup refines extremely unstable and is prone to oscillations, divergence and being stuck in false minima. This is true already under ideal conditions, where the elements in question provide decent contrast. Fe, Co, and Zn are very similar in scattering power, so that I doubt that reliable results could be obtained. This could be dealt with by doing either neutron or anomalous diffraction, which would provide data sets with different scattering factors. Am 20.02.2017 16:54, schrieb David MARTINEZ BLANCO: Dear Rietvelds, I recently find several manuscript that show some results about the cationic distribution on composition (Zn1-xCox)Fe2O4 using Rietveld method implemented on programs as MAUD, FULLPROF or GSAS. I am regular user of some of them and I can carry out this type of refinement when a tetrahedral and/or octahedral site contains only two different elements but I do not know how to perform when both interstices have the three different elements (Co, Zn and Fe), because I have only 5 equations, using composition and occupancy site relations, which 4 constrains are derivate from. Being 6 partial occupation necessary, I think that 2 parameters will refine but I have no idea how can write the equations in the previous programs. Could a brilliant mind send me the corresponding script (for example in Fullprof)? I greatly appreciate your help. Kind regards, David ________________________________ Helmholtz-Zentrum Berlin für Materialien und Energie GmbH Mitglied der Hermann von Helmholtz-Gemeinschaft Deutscher Forschungszentren e.V. Aufsichtsrat: Vorsitzender Dr. Karl Eugen Huthmacher, stv. Vorsitzende Dr. Jutta Koch-Unterseher Geschäftsführung: Prof. Dr. Anke Rita Kaysser-Pyzalla, Thomas Frederking Sitz Berlin, AG Charlottenburg, 89 HRB 5583 Postadresse: Hahn-Meitner-Platz 1 D-14109 Berlin http://www.helmholtz-berlin.de
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Please do NOT attach files to the whole list <alan.he...@neutronoptics.com> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
