Re: [sdpd] Reference materials for calibration and indexing

[L.M.D.Cranswick...@dl.ac.uk]

> Some annealing seems necessary if you compare the
> FWHMs (° 2-theta) of In2O3 and CeO2 recently distributed by
> D. Balzar for his Size/strain Round Robin (recorded in "exactly"
> the same conditions). There is one Y2O3 too in Powbase, not
> annealed. Also is given an Y2O3-a got with the Koalariet package,
> probably annealed (?) :
> 
>          In2O3         CeO2        2-theta         Y2O3    Y2O3-a
>          0.061           0.056         30.5        0.104      0.112
>          0.076           0.060         51.0        0.111      0.107
>          0.092           0.064         69.4        0.124      0.106
>          0.116           0.071         89.8        0.147      0.114
>          0.150           0.084        110.1       0.190      0.140
>          0.207           0.110        130.2       0.260

The Y2O3 is annealed (1200 C for around two to three days?) - 
according to the equations of XFIT/Koalariet it
has near zero strain and around 3000 Angstrom average crystallite
size.  It can refine on the common slit settings quite accurately
which is the thing that interests me.

What is the average size/strain results determined on the In2O3 or
is this what the round robin will give?

> >Is it possible to get a "fixed" slit data collection of this
> >where all the slit and geometry settings are noted?
> 
> Recording conditions were : Bragg Brentano geometry, Cu-Kalpha, 
> graphite monochromator in the diffracted beam, Soller 2°, variable
> slits ensuring a constant 6mm illumination of the sample surface, 
> Soller 2°, receiving slit 0.1mm.  The pattern in PowBase is corrected
> by 1/(sin theta) and so is already equivalent to a "fixed" slit data collection.
> 
> >I would be quite eager to try out a Fundamental Parameters
> >fit using Koalariet/XFIT.
> 
> Why exactly the FP approach cannot deal with that variable
> slits geometry ?

Sorry - forgot that it can - matter of habit in using fixed 
slit.  XFIT can do Variable slit (not really used it) - but 
old biases against variable slits die hard.

Lachlan.

-- 
Lachlan M. D. Cranswick

Collaborative Computational Project No 14 (CCP14)
    for Single Crystal and Powder Diffraction
Daresbury Laboratory, Warrington, WA4 4AD U.K
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