[Ifeffit] Question about mixed second coordination shell

[Otal Eugenio]

Dear Robert,
Thanks for your detailed answer.
I am cutting at R=3.35. I also tried to go up to 4.0 to provide more
freedom and to include the SS TM-O at 3.6.
It seems that including MS was not fruitful at the moment. I found the
contribution very tiny, Importance < 10.
I included the path at 3.6, and it fits well, but when I include the Na,
the CN_Na goes to high values (>10) and errors (~+/- 50)
I also tried to restrict the CN of TM to force the Na to take place and get
good results. Also useless.
I was checking the data in R_real and the TM and Na paths. I see the TM
path is in phase while the Na path is not. I wonder if this is affecting
the fit. How should I constrain the fitting to solve this situation?
Best regards.

[image: image.png]



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Eugenio H. OTAL
Assistant Professor
Dept. of Materials Chemistry
Shinshu University
4-17-1 Wakasato, Nagano 380-8553, JAPAN
eugenio_otal at shinshu-u.ac.jp
https://sites.google.com/view/zettsu-laboratory/news-updates

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On Wed, Jan 17, 2024 at 1:24 AM Robert Gordon <ragordon at alumni.sfu.ca>
wrote:

> Hi Otal,
>
> I ran a quick FEFF simulation just to see what is present under that
> second peak in the FT.
> There are many more shells than just TM and Na...e.g.
>
>
> There is significant multiple scattering and another backscattering peak
> (Fe-O) at
> 3.6Angstroms. All of these are going to spread underneath that peak in the
> FT. You might
> also be getting some interference from the 4.07A MS stuff. It doesn't seem
> a surprise that
> just including TM and Na is giving problems.
>
> What is your high-R cutoff? Have you tried including multiple-scattering
> or that 4th backscattering
> contribution?
>
> cheers,
> Robert
>
> On 2024-01-09 12:06 a.m., Otal Eugenio wrote:
>
> Dear all,
> Happy New Year!
> I am dealing with the fitting of NaMn0.3Fe0.4Ni0.3O2 second shell.
> I have Mn, Ni, and Fe at 2.9772Å and Na at 3.1859Å, showing only one
> shell. If I use any of the transition metals (dZ <5) for fitting the second
> coordination shell. fitting is fine, but when I introduce the Na path, the
> fitting has no sense, CN_Na grows and also its error.
> Even including Na, I have Nvary = 10 and Ninp = 13.98, so I am getting out
> of ideas and nothing helpful in the ifeffit Archive until now.
> Is there any strategy for dealing with mixed second coordination shells? I
> am attaching the file exported from Larch and the cif file.
> Best regards.
>
>
> (^ㅇᆽㅇ^)(=˃ᆺ˂=)(=🝦 ༝ 🝦=)
>
> Eugenio H. OTAL
> Assistant Professor
> Dept. of Materials Chemistry
> Shinshu University
> 4-17-1 Wakasato, Nagano 380-8553, JAPAN
> eugenio_otal at shinshu-u.ac.jp
> https://sites.google.com/view/zettsu-laboratory/news-updates
>
> ¯\_(ツ)_/¯¯\_(ツ)_/¯
>
> Who is John Galt?
>
> ¯\_(ツ)_/¯¯\_(ツ)_/¯
>
>
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