Hi everyone,
Three responses saying it might be a lower spacegroup? I wonder if the
emperors have their clothes on today?
(006) reflections can't split in R-3c as they only have a multiplicity
of 2 in the first place (0,0,6 and 0,0,-6). You were lucky enough to
split (00l) which rules out any lattice distortion. Or lots of people
are about to shout at me.
Either a paper about "phase segregation" or an experimental artifact
like a temperature instability. Or both!
Cheers,
Jon
[EMAIL PROTECTED] wrote:
Dear all
I need your kind help
I am investigating a trigonal system. I collected neutron diffraction
patterns at T=300K and T=4K.
The data at T=300K can be nicely fitted with the spg R-3c.
At T=4K again I can described the data with the spg R-3c, but I noticed that now
the peaks with a larger c-axis component (see the (006) peak picture in
attachment) are splitted in two: it is like as at low temperature there are two
phases with different c-axis (10.5838 and 10.566 Amstrong) and same a-axis.
I don't think that the sample is chemically phase separated because at room
temperature the (006) reflection is clearly a single peak. The splitting
appears only at low temperature.
Could anyone suggest me any possible explanation of this splitting (lattice
distortion, modulation, etc)? Could be possible a triclinic distortion?
I don't know how to fit the data at T=4K. Should I change the space group
because now I have two peaks while the R-3c gives me only one peak? Then by
which criteria should I choose the new space group?
thank you very very very much for your advices
best regards
Stefano Agrestini
Physics Department
The University of Warwick, UK
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