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

[Carlos Triana Estupinan]

Dear Yuanpeng,

Could I have a copy of the yet-to-be-released version of the package
that do the Fourier transform internally in RMCProfile along with
an example about how to use the the keyword to do the fit in real space. I
am using Mac OSX operating system

Thanks for your help

Best Regards,


2018-05-17 16:57 GMT+02:00 Yuanpeng Zhang <zhangy3 at ornl.gov>:

> Hi Clemens,
>
> In the current public release of RMCProfile, it seems that we do have some
> problems with the normalization for X-ray data due to the q-dependent form
> factors. Therefore the normalization may not be so straightforward as it is
> for neutron. Actually, if you have a look at the manual in the section
> introducing the 'XRAY_REAL_SPACE_DATA' keyword, you may probably notice
> that we have different options for the normalization.
>
> I have ever looked at your attached pictures showing the problem you
> described, but since the mailing list gets rid of the attachment so I
> cannot see it now. So can I ask you to share with me (email:
> zhangy3 at ornl.gov) your previously attached pictures? Also could you
> please share with the whole folder in which you ran the RMCProfile so I can
> have a look and see whether I can help solving the problem? Thank you!
>
> Meanwhile, we are currently working on a new way for the X-ray data
> fitting in RMCProfile, and in the new version we do the Fourier transform
> internally in RMCProfile so we don't need to provide the real space data by
> ourselves. The only thing we need is to provide the reciprocal space data
> and give the program a keyword saying we also want to fit in real space.
> The program now is not available to public yet, but if you want to have a
> try, I can send the package to you (if you tell me which operating system
> you are using).
>
> Cheers,
> Yuanpeng
>
>
> *Dr. Yuanpeng Zhang*
> Postdoctoral Research Associate
> Chemical and Engineering Materials Division
> Neutron Science Directorate
>
> Oak Ridge National Laboratory
> 1 Bethel Valley Road
> Bldg. 8600, Room C-509-C, Mailstop 6454
> Oak Ridge, TN 37831-6475
> Mobile | 865-335-4818
> Email | zhangy3 at ornl.gov <mailto:zhangy3 at ornl.gov> | Web |
> aipeng1990.life <http://aipeng1990.life>
>
> On 05/15/2018 08:30 AM, Clemens Prescher wrote:
>
>> 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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-- 


*Carlos Augusto Triana Estupiñan**PhD.*
* M.Sc. Sciences - **Physics*
*Physicist*
* Tel: +57 322 256-2309*
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