[Ifeffit] Fitting mechanism of Artemis

[Edmund Welter]

Dear Konstantin,

why would you want to do that? If you change the distance between A-B 
you the distance between B-A changes by the same amount. If you move the 
absorber away from let's say the centre of an octaeder you would split 
the (next) nearest neighbours shell into different shells with different 
distances. If the differences are large enough and the resolution of 
your EXAFS spectrum sufficient you would see more than one (first 
neighbours) peak in the FT of your EXAFS spectrum. But that would be 
another model that you would feed into FEFF before you start your second 
fit. Technically you would fneed to define the position of all atoms in 
your model in world-coordinates. So the absorber would no longer be at 
0,0,0. I would guess that this would make the computation and the model 
more complex or at least less intuitive.

Best regards,

Edmund


On 06.10.23 10:09, bikov at phys.uni-sofia.bg wrote:
> Dear all,
> I have a general question regarding the mechanism employed in the fitting
> procedures implemented in Artemis.
> How exactly is performed a fit? Do we have a fixed
> central atom (absorbing/emitting atom) and only the distances to the
> neighbors included in the probed pathways are varied, i.e. by varying the
> coordinates of the corresponding neighbor atoms, or during
> the fitting process Artemis can vary the position of the absorption center
> too? Could the procedure be constrained in such a way that the scattering
> pathways are adjusted by only varying the coordinates of the central atom?
>
> With kind regards,
> Konstantin Bikov
> PhD Student at the Physics Department
> of the University of Sofia, Bulgaria
>
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