Dear All,
I have several synchrotron X-ray data sets collected at different
wavelengths (as well as TOF neutron and standard Cu Xray radiation). The
pattern of the single phase material I am trying to refine contains both
strong sharp 'subcell' peaks and weak broad 'supercell' peaks.
The subcell reflections are those allowed in R-3m and the supercell
reflections are the extra reflections generated by lowering to P-3m
(i.e. p-3m reflections -R-3m reflections)
I would like to refine structures using a combination of all the data
sets and account for both these types of reflections and also be able to
include f' and f'' values.
Therefore I'm looking for a "Rietveld" program that can deal with all
the following options:-
1. At least two profile functions to fit the two types of peaks in each
histogram, preferably by assigning reflection conditions for paticular
classes of reflections to the paticular profile functions.
2. enable the use of multiple histograms (in particular with different
wavelengths)
3. deal with anomalous scattering data ie able to input f' and f''.
I have already looked at using GSAS and the constant wavelength profile
function 3 which gives the option of using stacking vectors but so far
have been unable to improve the fit of the broad reflections. I have
also considered using Rietan and although it offers partial profile
relaxation for a number of reflections and the capability of including
f' and f'' it cannot handle multiple histograms with different
wavelengths.
Does such a program with the listed criteria, exist? Any suggestions or
comments would be much appreciated.
regards,
Sandra Moussa
Department of Chemistry
Liverpool University
