[Ifeffit] Silent Oxygen

[Fuxiang Zhang]

Dear Bruce and Robert,
Thank you very much for the help.

Fuxiang

On Tue, Apr 18, 2017 at 9:10 PM, Robert Gordon <ragordon at alumni.sfu.ca>
wrote:

> Hi Fuxiang,
>
> Further to Bruce's note, I looked at your file. Your model splits the
> nearest oxygens by only 0.01A.
> Is that the magnitude of splitting you anticipate?
> Are you familiar with the resolution criteria for EXAFS?
> (k-range [deltak]) * (R-resolution [deltaR]) ~ pi/2 for identical near
> neighbours
> This is also discussed in the archives, e.g.:
> http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2007-Nove
> mber/003414.html
>
> Looking at your chi(k), it seems usable, charitably, up to about 8 A-1,
> not to 12 A-1 as your
> window suggests you have used. Claims of being able to resolve small
> splittings
> with this data will be viewed with skepticism.
>
> -R.
>
> On 4/18/2017 11:34 AM, Bruce Ravel wrote:
>
>> On 04/18/2017 11:10 AM, Fuxiang Zhang wrote:
>>
>>> Hi, all,
>>> I am in studying the EXAFS of perovskite and clearly see the split of
>>> the first peak after ion irradiation. It should come from a symmetry
>>> change, so I use a tetragonal model (instead the original cubic) which
>>> contains two independent O sites. However, after running Atoms and
>>> Feff, all paths are contributed by only one O atom and nothing related
>>> to another Oxygen atoms (see attached file). As a result it may
>>> be difficult to get a good fit of the first split Ta-O peaks. I am not
>>> sure if it is true or something wrong.
>>> Thank you very much
>>>
>>
>> A fairly common question here on the mailing list.  This is a *feature*
>> of Artemis, not a bug.
>>
>> http://bruceravel.github.io/demeter/documents/Artemis/extended/fuzzy.html
>>
>> If you want to /model/ a split in distance, you can drag that path into
>> the path list twice and adjust the delta R and amplitude parameters
>> accordingly.
>>
>> B
>>
>>
>>
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