[RMCProfile-users] Some stupid question：Using RMCProfile For X-ray synchrotron Data

[Nicholas Funnell]

Dear Bo,

1. You are right that the real and reciprocal space formalisms are different between the the PDFGet suite and GUDRUN. In the past, I have also done the same as you - dividing F(Q) by Q and using G(r) as a D(r). It would be a good idea to use a fitted scale on both datasets if you are doing this. 

2. Sorry, I don’t know enough about PDFGetX to do this - I use GUDRUN for my data normalisation. Perhaps someone else will be able to answer this?

3. There is no right answer to this question! The weight simply determines how strongly each dataset is going to drive the refinement - there is probably some trial and error involved here, and probably depends on what sort of features you are looking for. (The lower the value of the weight, the stronger the weighting). I would have thought that using 1000 and 0.01 as your respective weights is a bit extreme - typically I tend to upweight my reciprocal space data by an order of magnitude relative to my real space, but this is really dependent on the system you’re looking at and how much you trust your data.

4. You haven’t asked a stupid question, so I can’t answer that!

Hope this helps,

Best wishes,
Nick


> On 4 Oct 2015, at 20:49, Bo Jiang <youqin5912 at gmail.com> wrote:
> 
> Hi everyone,
>        I am working with PDF data collected from X-ray synchrotron source
> from ESRF, and I use the PDFgetx3 to produce the G(r) and F(q) file. But I
> face some problems like below:
> 
> 1)  I noticed that the definition of G(r) and F(q) from PDFgetx3 are very
> different to RMCProfile. I tried use D(r) and the F(Q) divide Q according to
> the equation 4.11 in manual, is that right?  
> 
> 2) In the Appendix B in tutorial version 6.5.2, it says that 'You will need
> to normalise your X-ray G(r) so that it is scaled from 0 to 1', does it need
> to be done? how to do it?
> 
> 3) Is there any trick for the setting of 'weight' for Bragg, REAL and
> RECIPROCAL, I use 1000, nd 0.01 for them.
> 
> 4)why always no one can ever answer my stupid questions? 
> 
> Thank you very much!
> 
> Bo
> 
> 
> 
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----------------------------------------------------------------------
Nicholas Funnell
Post-Doctoral Research Associate (Goodwin Group)
Inorganic Chemistry Laboratory
University of Oxford
Phone: 01865 272698