[RMCProfile-users] about using RMCProfile to simulate PDFgetX3 S(Q) and G(r)

[Martin Dove]

Hi

In the RMCprofile manual there is a section defining all the functions that RMCprofile uses, particularly with regard to the values at the limits (r = 0 or Q = 0, and r or Q going to infinity). These are the ways to best identify what the functions are rather than by name, because as my friend David Keen has written about, terminology in this field is not consistent and has a strong geographical bias.

So yes, D(r) in RMCprofile is G(r) in PDFgetX. I am not sure without checking about the scattering function, but I imagine so (RMCprofile will call this function i(Q)).

The D(r) and i(Q) terminology is from the UK from a long time before PDF work was fashionable. Personally I never quite liked F(Q) because F is also used in a very different way in crystallography, so it is better to keep it the same, and also I reckon that G(r) should be of the same sort of form as g(r). But this is only personal and goes beyond answering your question.

Best wishes

Martin Dove

> On 26 Oct 2017, at 12:31, 姚伟鑫 <yaoweixin at sjtu.edu.cn> wrote:
> 
> Dear all
> 
> Hello everyone!
> 
> I am using RMCProfile to simulate my PDFgetX3 S(Q) and G(r), but I have noticed that they are quite different from that in the RMCProfile manual. So I want to ask you that is PDFgetX3 G(r)=RMCProfile D(r)? And is RMCProfile F(Q)=PDFgetX3 (S(Q)-1)? 
> 
> Thank you very much!
> 
> Yours sincerely,
> Weixin Yao
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–––––––––––––––––––––––––––––––––––––––––––––––––––––––––
Martin Dove
School of Physics and Astronomy, and Materials Research Institute
Queen Mary University of London
Mile End Road, London E1 4NS
Tel. 020 7882 3426