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Re: [sdpd] Indexing Problem
Hi,
Without seeing patterns and fits, the diagnostic is uncertain.
But the indexing FoMs are quite not satisfying (too small), and
the Le Bail fit Rwp is too high for being convincing enough.
Note that when a pattern is a low-quality one with noise, you
may have such small FoMs and high Rwp even if the cell is
correct. But the ideal situation is really to have high FoMs and
small Rwp...
The conclusion is : if your pattern is a low quality one, then record
a better one and see if the FoMs and Rwp improve. Maybe you will
obtain another cell when indexing again...
Your question about these two major peaks is not clear. If the
output gives "|Fobs|", they are changed a lot if compared to intensities
on the raw pattern. But, are these peaks well fitted, aren't they
belonging to an impurity, etc ?
Best,
Armel
At 12:25 30/01/2011, you wrote:
>Hello
>
>I want to determine the crystal structure of small organic compound
>form powder diffraction data which has been collected by STOE
>diffractometer. In fact, I use DICVOL, ITO, TREOR, and MCMaille
>program and the results of Dicvol and MacMaille indicated to
>Monoclinic system with a=10.78, b=11.30, c=17.68 and beta=119.40
>M(18)=11 F(18)=20 parameters. When I use this cell parameters in the
>solution stage with FOX software and choose the P2/c space group (Le
>Bail fit 17% Rwp), in the optimization process, the low angle of
>pattern match well until 25 degree(2theta) but the higher angle
>which contain two major peaks with highest intensities have the very
>low intensity in the Bragg reflection related to these peaks.
>
>I don't know, does the problem relate to unit cell or space group?
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