[Ifeffit] Fwd: scattering amplitude by FEFF and Artemis

[Feng Wang]

Thank you, Dr. Ravel,

Could you please just simply tell me the expression for the magnitude of chi
(q) (labelled as |chi(q)|)? Thank you.

Feng


> Feng,
> 
> I am forwarding this to the Ifeffit mailing list since I am in the
> middle of an experiment and don't have much time to devote to an
> answer. 
> 
> > Dear Dr. Ravel,
> 
> > I am now learning to use your Artemis program to calculate the 
scattering 
> > amplitude from each paths (shells). It seems your Artemis can give the 
> > scattering amplitude of each path, as done by EXAFS calculations in 
FEFF. I 
> > think the results from both program should be same or comparable, but it 
> > looks much different, as attached for a result of diamond-K. Is anything 
> > wrong with my calculations?
> 
> It's really hard to tell.  The figure you sent does not convey any
> sense of how it was made.  Without a clear explanation of what you
> did or, better yet, an artemis project file to inspect, I am not sure
> how I can possibly answer your question.
> 
> > I have been wondering how big a cluster we should use for FEFF 
calculations, 
> > or the contributions of the atoms far from the central atom (e.g. > 1nm) 
> > since so big clusters (such as 400 atoms and even more) are used for 
FEFF 
> > calculations in several recent publications. I hope to get some ideas 
from 
> > the scattering amplitude of the paths involved by the atoms far from the 
> > central atoms. Do you also have any suggestions? 
> 
> The nice thing about feff is that it is very easy to use to answer
> this sort of question without having to rely on an "expert".  What
> happens if you run feff with clusters ranging from very small to very
> large and compare the chi(k) functions generated for the first few
> coordination shells?
> 
> B
> 
> > Feng
> 
> > ====================================
> > EM group, NINT
> > 11421 Saskatachewan Drive
> > Edmonton, Canada T6G 2M9
> 
> -- 
>  Bruce Ravel  ---------------------------------------------- bravel at anl.gov
> 
>  Molecular Environmental Science Group, Building 203, Room E-165
>  MRCAT, Sector 10, Advanced Photon Source, Building 433, Room B007
> 
>  Argonne National Laboratory         phone and voice mail: (1) 630 252 5033
>  Argonne IL 60439, USA                                fax: (1) 630 252 9793
> 
>  My homepage:    http://cars9.uchicago.edu/~ravel 
>  EXAFS software: http://cars9.uchicago.edu/~ravel/software/



====================================
EM group, NINT
11421 Saskatachewan Drive
Edmonton, Canada T6G 2M9