ben1980 Hi guys, I would like to know if it is possible to refine site occupancy in my composition using TOPAS 4.2. This composition is basically Nax(Mn0.44Fe0.56)O2 with Mn/Fe possibly distributed in FIVE different Wyckoff sites. So I am wondering if there are some parameter constraints for refining Mn/Fe occupancy at these FIVE sites and keeping the stoichiometry of Mn0.44Fe0.56? Cheers
johnsoevans You can write any set of equations you think appropriate, but (of course) you need to make sure that the data contain the information you are trying to refine. To control overall composition you might find it easiest to use a restraint rather than a constraint.
joanna-naomi I have several sites that are occupied by Al and Si. I have made the Al site occupancies different parameters eg xal1, xal2, and made the Si site occupancies dependent on them eg =1-xal1, so far so good. Now I am trying to add a constraint whereby the total amount of Al across all sites is limited to 1. Directly after the site information in my INP file I have added the line prm alpc = xal1 + xal2 + xal3; when I try to load my file into topas it returns the error *** Error loading sstring_in at { prm } unknown or misplaced keyword. at LINE 71 See log file C:\TOPAS4-2\topas.log when I check the log file it shows just prm alpc = xal1 + xal2 + xal3; can anyone give me any pointers here?
alancoelho Joanna Can you send the INP and data file (email: AlanCoelho@bigpond.com) and I will have a look. cheers
fredmarlton Hey, was there ever a solution posted to this? I'm trying to do a split-atom model with 4 different occupancies and the following constraint; a + b + c + d = 1 But I'm finding it a little difficult to get that constraint to work. Any tips much appreciated. Thanks, Fred
fredmarlton Just found the following example, so should be ok.... for now. test_examples\occ-constrain.inp