Is it possible that some of these offending datasets that
are not fitting nicely can be put on the web somewhere
so they can be tried out?
The CCP14 web area is open for such things if required.
I generally have no trouble fitting the entire pattern
with Fullprof and LHPM/Rietica using Le Bailing fitting
and the FCJ Asymmetry correction. Though misalignment
of the diffractometer would be my first choice to look
into.
On the note about using more appropriate slits to minimise
peak asymmetry. As the new algorithms fit asymmetry very
well in my experience - this can be used to advantage to
allow insertion of coarser Sollers slits to raise the
intensity (lowering counting time) and also helping with
particle statistics.
Lachlan.
> Patrick Weisbecker wrote:
>
> > Hello,
> >
> > About influence of misalignement on peak assymetry; A good mean to
> improve
> > symetry of peaks at low angles is to use soller slits, indeed other
> > parameters than alignement can be responsible for asymetry.
> >
> > As for modeling peak shape, I use Fullprof and i also have
> difficulties to
> > find a good agreement between experimental and calculated pattern
> because
> > of asymetry at low angles.
> > If someone knows if a particular profile (on this sofware) is best
> suited
> > for asymetry i will appreciate.
>
> I find FULLPROF works OK if I split the pattern up into 2 segments.
> Below 20
> two theta (using CuKalpha) and greater than 20 two theta and fit
> asymmetry
> seperatly for the two sets of data. The asymmetry parameters dont seem
> to be
> very effective if one attempts to match the entire pattern
> simultaneously.
>
>
> >
> >
> > Patrick
>
>
>
> --
> ****************************************************************************
>
> Bruce A. Weir,
> Optoelectronics,
> Cavendish Laboratory,
> University Of Cambridge,
> Madingley Rd,
> Cambridge,
> CB3 0HE
> U.K.
>
> Tel: +44 01223 337285
> http://www.geocities.com/timessquare/bunker/6614
> ****************************************************************************
>
> "She had a pretty gift for quotation,
> which is a serviceable substitute for wit."
> - - - W. Somerset Maugham
>
>
--
Lachlan M. D. Cranswick
4th Jan - 16th March 1999 Visiting Scientist
CSIRO Division of Minerals, Melbourne, Australia
Tel: (613) 9545 8500 (switch)
Fax: (613) 9562 8919 [EMAIL PROTECTED]
Collaborative Computational Project No 14 (CCP14)
for Single Crystal and Powder Diffraction
Daresbury Laboratory, Warrington, WA4 4AD U.K
Tel: +44-1925-603703 Fax: +44-1925-603124
E-mail: [EMAIL PROTECTED] Ext: 3703 Room C14
NEW CCP14 Web Domain (Under heavy construction):
http://www.ccp14.ac.uk
