[Ifeffit] Ti data problem
segre at iit.edu
Mon Aug 8 16:37:56 CDT 2016
For the first one of the spectra, I chose the shoulder in the derivative
at 4974 instead of the large peak. I consider the lower energy peak to be
a pre-edge feature due to the 3d quadrupole transitions and I generally
don't choose that. If the analysis later tells me that I am wrong, I move
In this case, the 4974 positoin withthe other parameters I mentioned gives
a very reasonable FT.
On Mon, 8 Aug 2016, Qingying Jia wrote:
> 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.
> 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?
>> 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
>>> 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:
>>> 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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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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