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RE: [sdpd] Indexing problem
Dear Christian,
What is the quality of the low-temperature fit? I was thinking that you could experience a temperature dependent shift of the sample surface. Is that possible?
Best regards,
Jens
> -----Original Message-----
> From: Cristian Perca [mailto:cristianperca...@yahoo.com]
> Sent: 18. november 2004 19:43
> To: sdpd...@yahoogroups.com
> Subject: [sdpd] Indexing problem
>
>
>
> Dear all,
> I encounter a (serious) problem when trying to index an X-ray
> powder pattern. The data was measured on a good
> diffractometer (Philips X-celerator, Cu
> Kalpha1;-Brag-Brentano geometry) (lowest FWHM~0.06 °) with a
> step of 0.016° and a lot of counting time. The sample has a
> perovskite like structure and undergoes a number of
> structural transitions when heating. Triclinic at room
> temperature (I have refined this one), unknown intermediary
> temperature phase, and a tetragonal high temperature phase (I
> have refined this one too). When indexing with the majority
> of the available software (Dicvol, Treor,
> Ito...) alone or in the Crysfire suite, in the front of the list I get a
> monoclinic cell a=7.86 b=7.68 c= 7.72 A and Beta~90.3°
> with rather good
> agreement factors (M20 about 180). Refining the cell in
> FullProf, gives a perfect fit for the low 2Theta pattern
> (2Theta<80°), but at high 2Theta values there are some shifts
> in the positions or the reflections.
> I have thought that this could came from some instrumental
> error, but the tetragonal high temperature phase give a
> perfect fit even in this are, so I have excluded this possibility.
>
> Is someone has any idea or maybe has encountered the same
> kind of problem, please help me. Thank you in advance
>
>
> =====
> Cristian PERCA
> Laboratoire de Physico-Chimie de l'Etat Solide
> Bât. 414 - Université Paris XI
> 91405 ORSAY Cedex - France
> http://www.u-psud.fr/chimsol
> Tél : 01 69 15 48 04
> cristian.perca...@lpces.u-psud.fr
> cristianperca...@yahoo.com
>
>
>
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