EXPGUI and constraints?

[Christoph Salzmann]

Dear all,   I'm using the EXPGUI software to refine the structure of a monoclinic phase of ice. (ice V) The diffractograms were recorded on the D2B instrument at the ILL. As a result of this study, we would like to see changes in the occupancies of the deuteria positions.   Due to the low symmetry of this phase, I have to use some constraints during the refinement. There are 14 different sites of deuteria in this phase. If the stochiometry of this phase is taken into account, the occupancies can be described by only 4 ordering parameters. I'm now reaching the limits of the "Constraints" function in EXPGUI: I can refine the single ordering parameters. But additionally, all four ordering parameters should add up to 4. This seems to be impossible in EXGUI?   So my question: Can I use the EXGUI software AND define further constraints in GSAS? How can I do this?   Thank you very much for your help in advance!   Yours, Christoph      ----------------------------------------------- Dr. Christoph G. Salzmann Institute of General, Inorganic and Theoretical Chemistry Innrain 52a University of Innsbruck 6020 Innsbruck Austria / Europe e-mail: [EMAIL PROTECTED] phone: +43 512 507 5122 fax: +43 512 507 2934 -----------------------------------------------