As a rule, before doing that I'd switch to xye format to preserve the
statistics
Wow. What a rule.
Did anyone try to calculate simple mean deviance and compare with
popular R factors?
OS
*From:* Whitfield, Pamela [mailto:pamela.whitfi...@nrc-cnrc.gc.ca]
*Sent:* Wednesday, March 04, 2009 8:17 AM
*To:* Jon Wright; olga.smirn...@hw7.ecs.kyoto-u.ac.jp
*Cc:* rietveld_l@ill.fr
*Subject:* RE: cRs
I'll put my tuppence worth in here as there can be another
consideration with high backgrounds.
Normally I wouldn't touch the background, but there are times when a
high background causes an artificially shallow minimum and the
refinement isn't going very far (Rietveld software is usually
minimizing Rwp so starting out with a low Rwp isn't very good).
In this instance making the Rwp worse when the peaks aren't fitting
can help. As a rule, before doing that I'd switch to xye format to
preserve the statistics before doing a linear, across-the-board count
substraction (not attempting to take out any wiggles which will
distort peak shapes, etc - leave that to the background modelling). I
suppose you may introduce some slight distortions into the result but
if the refinement is going nowhere then....
However if you try this approach your final Rwp may end
up significantly worse than other papers in the literature, and there
are occasions when referees can get hung up on residuals when
a difference plot speaks a thousand words (or numbers). I suppose you
could always go back and fit the refined model to the original data to
get a wonderful, if slightly meaningless Rwp for the paper!
Pam
