Dear everyone,
Hi, i am a new user of the Rietveld refinement. Currently my
interest is in the extraction of size/strain information from the line
broadening profile of XRD pattern. The substance i am working on
is organic Paracetamol powder.
I am confused by the concept/definition of the size, which is
expressed as the 'coherent domain size, or weighted mean of
length of columns of unit cells in the direction parallel to the
diffraction vector, averaged within domains and throughout the
samples' . My questions are:-
a) what is/are the difference(s) between this 'size' compared to the
size measured by other, mostly optical, methods? (such as laser-
size analyser?) Is the difference orginated from the direction of the
measurement of size, in which the direction from size analysis by
line broadening is fixed to be parallel to diffraction vector; while the
size analysers only take the longest dimension in a random
manner?
b) if the size effect in the line broadening of the whole powder
diffraction pattern is taken as isotropic, then which direction is the
<D> taken for (normal to which diffraction vector) in the analysis?
Any help/advice would be very much appreciated. Thanks in
advance.
Chun Min
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Chun Min CHEW
Particle Products Group
Department of Chemical & Process Engineering
University of Sheffield
Mappin Street
Sheffield S1 3JD
Telephone: (44)0114 222 7543
Fax: (44)0114 222 7501
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