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RE: [sdpd] Indexing problem
Hi
I don't think this has something to do with the temperature (not in this
way) because the low temperature and the high temperature (higher than
this one) give a perfect fit.
In fact, what i forgot to mention in the previous message, i am not sure
that is a pic shift, because at high angles the pic overlap is quite
important.
--- jens.wenzel.andreasen...@risoe.dk wrote:
> 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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=====
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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