[Ifeffit] Ti data problem

[Qingying Jia]

Hi Carlo,

  In many transition metal oxide cases like this, what would be the more
proper E0, the position of the apex of the first derivative peak or the
second one that is usually higher than the first peak, or it really
depends? I have seen people using either. In this particular case, it seems
like using E0 of 4967 eV (the first derivative peak position) gives cleaner
and more reasonable FT-EXAFS.

  Regards,
  Jia

On Mon, Aug 8, 2016 at 5:05 PM, Carlo Segre <segre at iit.edu> wrote:

>
> Hi Siliang:
>
> The first thing is that you have misidentified the edge position.  Itis
> way too high in all the data sets.
>
> Put it at the inflection point of the main rise in the absorption curve
> and you will find that the problem is much reduced.
>
> The second thing is that you have a very bad backgrund problem in your
> data and, in my estimation your usable data range is no moe than k=2 to
> k=8.  In fact, my suggestion is that you truncate the data by setting the
> spline range to end at 8.  The FT range should probably be set at 2-8 or
> even 2-7 (somewhere in that range and put a window sill of dk=2 to get rid
> of some of the ringing.
>
> Once you do those things the data will look much more reasonable.
>
> These data could probably have used some longer counting times.  Where did
> you take the data?
>
> Carlo
>
> On Mon, 8 Aug 2016, Siliang Chang wrote:
>
> Dear all,
>>
>>
>>
>> I am new to XAFS data analysis. I?m currently working on the XAFS data of
>> atomic layer deposited mixed oxide thin film: SnTiOx. I have both Sn and
>> Ti
>> K edge data, and was able to fit Sn edge using a model of (Sn,Ti)O2 solid
>> solution. However, Ti data really confuses me (please see attached file).
>> With Rbkg set to 1, there is a doublet in 1-2 Å region in every data, this
>> is something I have never seen in the literature. I?m wondering if this is
>> normal? Does this mean I should set a larger Rbkg value, say, around 1.5?
>>
>>
>>
>> I?ve tried to fit the abovementioned Ti data using several models:
>> anatase,
>> rutile, (Sn,Ti)O2 solid solution, perovskite (N is fixed at 6 for all of
>> those), so far no success. I would really appreciate if you can comment on
>> my data processing, any suggestions are welcomed, as I?m new to this, I?m
>> not sure if I?m doing it the right way.
>>
>>
>>
>> Thank you very much.
>>
>>
>>
>> Best regards,
>>
>> Siliang Chang
>>
>>
>>
>>
>>
>>
>>
> --
> Carlo U. Segre -- Duchossois Leadership Professor of Physics
> Interim Chair, Department of Chemistry
> 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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