Re: FEFF: Broadening

[Matt Newville <newville@cars.uchicago.edu>]

Hi,

>  P> Hello feffusers, I am investigating the system,
>  P> BaTiO3. Specifically l am looking at the elnes generated by the
>  P> xanes card. I would like to introduce broadening into my
>  P> calculation as it does not seem to converge, even for very big
>  P> clusters. If l increase Eimag for LDOS , (module two) will this be
>  P> carried through to the xanes calculation or is there another way
>  P> to introduce broadening?  Also, if this is the correct way to
>  P> introduce broadening and get the calculation to converge with
>  P> smaller clusters, then what would be an appropriate value for
>  P> Eimag?
>
> Paula,
>
> You might try making the calculation with no additional broadening and
> then use the CORRECTIONS keyword to convolve the final function with a
> post facto broadening term.

Is the additional broadening for ELNES due to energy resolution
in the analyzer?  If so, wouldn't this have a more Gaussian
broadening, while EIMAG and CORRECTIONS will be more
Lorenztian-like?  If the broadening is large enough, even
CORRECTIONS may never work well enough.   I believe the
diffraction community has been using modified Voight functions
for decades just because of these effects.

It would be nice to have a way to add experimental broadening
correctly in Feff  -- maybe someone has already done this???

--Matt