You seem to be confusing beq (thermal parameter) with site occupancy. At a start, I would think that the site would have the same thermal parameter for either atom, and refine occupancies that sum to unity. For example, site A1 occ Fe feocc .9 x 0 y 0 z Az .055 beq Abeq 2 site A2 occ Ru =1-feocc; x 0 y 0 z =Az; beq =Abeq; will put Fe and Ru in the same site, refine the iron occupancy (feocc), common z coordinate (Az), and give them the same isotropic thermal parameter (Abeq). You could imagine that the lighter atom could have a larger thermal parameter, but it would be very hard to determine that from powder data because it would be strongly correlated with site occupancy, etc.
************************** Peter W. Stephens Professor, Department of Physics and Astronomy Associate Dean for Curriculum, College of Arts and Sciences Stony Brook University (631) 632-8156 http://mini.physics.sunysb.edu/~pstephens Please update your records to my new email: peter.steph...@stonybrook.edu On Mon, Apr 28, 2014 at 7:39 AM, NAVEED ZAFAR <naveed...@hotmail.com> wrote: > > > *Dear Rietvelders,* > I was actually doing the site (occupancy) refinement using TOPAS 4.1 > software. > While studying the effect of doping on one crystallographic site. > > We normally refine the sites of interest employ the following methodology. > Consider e.g., Pervoskite structure (ABO3) as an example. > If we wish to dope the A site in ABO3, > and to confirm whether doping was successful or not, we normally refine > the occupancies in the following way. > > For example. > We refine occupancies like occupancy of original site A =beq1 > occupancy of dopant site A` =1-beq1 > > If the refinemnent goes well, all the crystallogrhic occupancies > should merge to a single constant value, > those crystallographic sites which are fully occupied should give [occ=1] > and those doped should yield net occupancies [occ (A + A`= 1]. > > Can anyone share or suggest, > why the Beq (isotropic temperature factor) values are going to huge,?? > at the end of such a refinement. Which otherwise should be around [ > Beq=Uiso*8pi^2]. > > Also if possible share .pro file (GUI mode or Launch mode) of such a > refinemnet or some literature. > > Best regards, > *Dr. Naveed Zafar Ali* > > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > 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/ > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > >
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 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/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
