Dear Peter,
Of course the LP correction can't be sample-dependent and for your
configuration LP=0 should be Ok for all samples. It seems that you have an
intensity loss at high-angles that may be partly compensated by LP=90. Possible
reason may be in a misalignment of the anti-scattering slits or screen (knife)
if you use them.
Best regards,
Leonid
*******************************************************
Leonid A. Solovyov
Institute of Chemistry and Chemical Technology
660049, K. Marx 42, Krasnoyarsk , Russia
www.icct.ru/eng/content/persons/Sol_LA
www.geocities.com/l_solovyov
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--- On Thu, 7/23/09, Peter Y. Zavalij <pzava...@umd.edu> wrote:
From: Peter Y. Zavalij <pzava...@umd.edu>
Subject: RE: LP factor in the Rietveld refinement
To: rietveld_l@ill.fr
Date: Thursday, July 23, 2009, 4:52 AM
Well... the situation with LP is not so simple. Using TOPAS for refinement
data collected on D8 advance with Ni-filter and LynxEye detector I observe
the following:
- For all samples LP=0 is OK and gives the best fit as it should be by the
book.
- HOWEVER for LaB6 standard LP=0 yields very poor fit for several high angle
reflections (>120 deg. 2theta) while LP=90 gives perfect fit. The difference
in R factors 12% and 4% cannot be simply ignored...
Can anyone explain this?
Peter Zavalij
X-ray Crystallographic Center
University of Maryland
College Park, MD
Office: (301)405-1861
Lab: (301)405-3230
Fax: (301)314-9121
