[Ifeffit] plotting anotation

[Bruce Ravel]

Hi Dr. Matsuura,

I am answering CCing this email to the Ifeffit Mailing List

  http://cars9.uchicago.edu/mailman/listinfo/ifeffit/

which is the most appropriate forum for asking questions about the
software.  If you have not yet joined the mailing list, we encourage
you to do so.

I have also taken the liberty of converting the image file you
attached into a format that everyone will be able to view.


On Tuesday 30 June 2009 02:49:51 am you wrote:
> Dear Bruce Ravel
>
> I'm a beginner of IFEFFIT.  I'm pleased if you could ask following
> questions about plotting in Artemis.
>
> 1)     In a plotted figure as attached, annotation shows "2/path #". What
> does it mean letter" 2".

Presumably, you have more than one Feff calculation in your Artemis
project, one of which still has its default name of "Feff2".  To save
horizontal space in the legend of the plot, I have Artemis drop the
ltters "Feff".  So, that legend entry means "Path N from Feff
calculation 2".

> 2)     In the plotted figure attached, the sum of each path constituent is
> not equal to fitting data. The reason of why.

In Ifeffit, we use a complex Fourier transform to convert chi(k) to
chi(R), thus chi(R) is a complex function.  When the fit is evaluated,
the real part of the theoretical chi(R) is compared to the real part
of the data chi(R) and the imaginary part is compared to the imaginary
part.

You have plotted the magnitude of this complex function.  You should
not expect the sum of the moduli of the paths to equal the modulus of
the sum of the paths.  For a complex function, summation and mudulus
are not commutative operations.

B


>
>
>
> ***************************************************************************
>* ******************
>
> Metallic Glass Inorganic Materials Joinning Technology Development
>
> Institute for Materials Research, Tohoku University,Sendai, 980-8577,Japan
>
> Dr. Makoto Matsuura
>
> e-mail:m_matsuura at imr.tohoku.ac.jp
>
> ***************************************************************************
>* *******************



-- 

 Bruce Ravel  ------------------------------------ bravel at bnl.gov

 National Institute of Standards and Technology
 Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
 Building 535A
 Upton NY, 11973

 My homepage:    http://xafs.org/BruceRavel
 EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/

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