-----
You may like to look at Bernhard Rupp's pcXLAT software for
Unit cell refinement as it gives a polynomical output
based on an internal standard that you could then correct on.
You may have to put in dummy data to refine on
to get it working - as I think it expects
to be applying this polynomical on something real.
Another option could be to randomly assign hkls for your unknown
peaks - for inputting into XLAT with the "standard peaks". This
would give a junk result for the refined cell - but would give
the corrected peak positions based on the polynomial it
determined from the internal silicon standard in the output file.
I think this makes sense(?)
These corrected peak positions can then be passed onto your indexing
program of preference.
(have not tried this myself but in theory should work)
To get XLAT:
ftp://www-structure.llnl.gov/
http://www.dl.ac.uk/CCP/CCP14/ccp/ccp14/ftp-mirror/llnlrupp/
----
Not sure if Nita Dragoe's Powder software (or a few others)
can also be tricked into doing this as well?
http://www.hongo.ecc.u-tokyo.ac.jp:10080/~tdragoe/soft.html
http://www.dl.ac.uk/CCP/CCP14/ccp/web-mirrors/ndragoe/~tdragoe/soft.html
Please give a summary of how you get on with this if possible?
There may be far slicker ways of doing this.
Lachlan.
PS: Not sure if this is an old trick for some - but I have been
having quite a bit of success applying the Le Bail method as a guide
for confirming space group assignments on powder data for ab-initio
work. Especially useful for highly overlapping/poor resolution
data by noting the total profile fit in comparison with related
space groups - such as in Energy Dispersive data, or poorly crystalline
material.
i.e., in the case of monoclinic: trying c2/m; c2/c; p21/m; p21/c, etc.
Check which gives the best fit and look closely at the
profile vs the calculated hkls.
Fullprof combined with the latest WinPlotR has been found to be
quite effective - though have to keep remembering to set Irf flag
back to zero - or you get into a world of pain as it uses
the HKL file from the previous spacegroup. Though any Rietveld
program that supports Le Bail extraction should work.
List of programs (please suggest updates of software not included) at:
http://www.dl.ac.uk/CCP/CCP14/solution/lebail/index.html
This method does seem to be aluded to in the fine print in the Structure
Solution from Powder Data tutorial at:
http://fluo.univ-lemans.fr:8001/iniref/tutorial/part222a.html
http://www.dl.ac.uk/CCP/CCP14/ccp/web-mirrors/armel/iniref/tutorial/part222a.html
>
> I am looking for a program for the correction of peak positions
> (Bragg-Brentano-G.) using an internal standard like silicon. I think the
> program should fit experimental and calculated peak positions of the
> standard using a polynom (and not only displacement or zero-shift).
> However, I am not looking for a rietveld-program, since the phase we
> want to index is yet unknown.
>
> Thanks in advance
>
> Dr. Stefan Kaskel
> Institut of Inorganic Chemistry
> University of Tuebingen
> Germany
>
-- Lachlan M. D. CranswickCollaborative Computational Project No 14 (CCP14) for Single Crystal and Powder DiffractionDaresbury Laboratory, Warrington, WA4 4AD U.KTel: +44-1925-603703 Fax: +44-1925-603124 E-mail: l.cranswick@dl.ac.uk Ext: 3703 Room C14CCP14 Webpage (Under heavy reconstruction): http://www.dl.ac.uk/CCP/CCP14/