[RMCProfile-users] G(r) from X-ray diffraction data

[James Drewitt]

Hi Clemens,


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But I think it needs a G(r) data file already offset, where the limit G(r<rmin)=-1 and G(r=infty)=0 then in the RMC input file you choose  > CONSTANT_OFFSET :: 0.000.


Let me know if it works, or send me a private e-mail if you need, I can send you my working directory with an example.


Best wishes,


James


___________________________________

Dr James Drewitt
Senior Research Associate

School of Earth Sciences,
University of Bristol, Wills Memorial Building,
Queens Road, Bristol, BS8 1RJ

Tel: +44(0) 117 954 5421
url: <http://seis.bris.ac.uk/~jd14363/> http://seis.bris.ac.uk/~jd14363/<http://seis.bris.ac.uk/~jd14363>
___________________________________

________________________________
From: rmcprofile-users <rmcprofile-users-bounces at shadow.nd.rl.ac.uk> on behalf of Clemens Prescher <clemens.prescher at gmail.com>
Sent: 15 May 2018 13:30:08
To: rmcprofile-users at rmcprofile.org
Subject: [RMCProfile-users] G(r) from X-ray diffraction data

Hi there,

i have problems figuring out how X-ray derived PDF should be correctly
inputted into RMCProfile.

On page 157 in the RMCProfile manual it is written that the X-ray G(r)
needs to be normalised so that it is scaled from 0 to 1. This is exactly
the format i have. However, if I init my calculation and plot the "PDFs of
rmc fit" using rmcplot it has an offset (please see the attached figure "
gr_without_offset.ps")

It is clear, that the RMC fit is actually normalized to 0 when going into
infinity.

I thought, this might just a result by subtracting 1 from the previously 0
to 1 normalized G(r). But after several iterations using an offset of -1 it
became clear that low part is not normlized to -1. (see the
"gr_with_offset" figure attached).

In the manual it is also written that G(r) goes from -(sum c_j b_j)² to 0.
But for X-ray this does not make sense due to q-dependent form factors...

Can you please explain me how i should transform my data?

Best wishes,
Clemens
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