At the ILL Powder meeting earlier this year
Juan Rodriguez-Carvajal was asked when/if Spherical
Harmonics might be put into Fullprof.
Juan's reply was more of the nature you should
try and do the best sample preparation possible
and get the best diffraction data possible rather
than try and model/fudge corrections into the data.
Seeing Spherical Harmonics in action in GSAS and Topas,
it is easy to see why people using Spherical Harmonics
must love this correction as it can make what looks
like quite a bad fit become exceptionally good at the
flick of a switch. Thus giving the impression that
something this good must be evil!?
Given Spherical Harmonics can have this affect at
making the fit look very nice, are there recommendations
on how to review results that have included
Spherical Harmonics corrections for preferred
orientation?
i.e.,
What is considered appropriate and worrying in terms
of the "order" used and values of the GSAS Texture
Index when using Spherical Harmonics?
Should people be providing before Spherical Harmonics and
after Spherical Harmonics goodness of fit plots for publication
and review? (possible the same should go for any use of
preferred orientation corrections?)
Lachlan.
--
Lachlan M. D. Cranswick
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
http://www.ccp14.ac.uk
