[Ifeffit] [Ext] Two phases EXAFS fitting-help

[Carlo Segre]

Hi Danting:

One way to do this is if you have separate EXAFS of the two components.  In
that case you can fit the two reference materials and then use the two
separate fit models with a fractional parameter to fit the sample.  The
initial way to do this would be to hold all the parameters of the two
separate models fixed initially and scale the amplitude of each with a
parameter that is constrained to add up to 1 for both.  You will have to
make sure you apply a scale to your two models so that they are both on a
per Zn atom basis.  If this is successful, then you can decide if it is
appropriate to relax some of the parameters of the individual models but
you might wish to be cautious with that.

Carlo

On Tue, Nov 10, 2020 at 7:00 AM Chen, Danting <danting.chen.19 at ucl.ac.uk>
wrote:

> Hi Mr/Ms,
>
>
>
> I have a sample and get a two major phases result by linear combination
> analysis, one dominate 59.5% of hydrozincite( and another is 33.5% zinc
> phosphate (. I would like to use Artemis to fit the k-space and the first
> shell of R-space.
>
> For R-space, my idea is to fit the first Zn-O shell since both dominate
> phases are both tetrahedral and octahedral coordination and the first shell
> is the similar environment.
>
> For k-space, shall I fit each phase with the sample individually and then
> sum the different weight of fitting curve together to see how it fit
> finally? If it is right, may I ask how exactly it fits? I have no idea how
> the weight is set in Artemis or it can only be summed half by half?
>
> Also, since my sample numbers are only two, I am unable to use PCA to fit.
> Except the above mentioned, is there anything else that I can do?
>
> Sorry, I am a new learner of XAS and have many things to learn.
>
>
>
> Best Wishes,
>
> Danting
>
>
>
> Sent from Mail <https://go.microsoft.com/fwlink/?LinkId=550986> for
> Windows 10
>
>
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-- 
Carlo U. Segre -- Duchossois Leadership Professor of Physics
Director, Center for Synchrotron Radiation Research and Instrumentation
Illinois Institute of Technology
Voice: 312.567.3498            Fax: 312.567.3494
segre at iit.edu   http://phys.iit.edu/~segre   segre at debian.org
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