[Ifeffit] chi.dat (was: Uing more than one E0??)

[Matt Newville]

Bruce said:

> It turns out that it is extremely well hidden.  Sufficiently well
> hidden that I had to start digging through the feff6L source code.
> 
> It seems that the last module (the one that writes chi.dat) is never
> called in feff6L.  Indeed, the call to the last module is commented
> out in the file feff.f.
> 
> Question for Matt:
>   Is there a reason that the call to ff2chi is commeted out in feff6L?
>   I just uncommented that block and, in the one case I tried, it ran
>   to completion.
> 
> If you would like to fix this by hand (you'll need a fortran
> compiler!), just go to the src/feff6/ folder in the ifeffit source
> code distribution and edit the file feff.f.  Right at the end is a
> comment out bit that starts "if (mchi .eq. 1)".  Uncomment that block,
> recompile, and move the excutable to its proper place in the path.
> Then "PRINT 1 0 0 0" will work just fine.

Feff6L does not calculate chi.dat because, as far as I can 
tell, chi.dat has no use.  With Ifeffit, the sum over paths 
is "trivial" (in the physicists sense of "not impossible"). 
With Artemis, it's actually easy.  It's better to do this 
step with Ifeffit/Artemis because you can use any number of 
paths you want (as for a spline() standard), add paths from 
different runs of Feff, put in sigma2 terms, etc, and get the 
outputs in any format, not the strange format of chi.dat.

Did you need it for something?  If so, I'd rather link feff6l 
with libifeffit and use Ifeffit's sum of path to reduce code 
with repeated functionality.

--Matt