[Ifeffit] Question about mixed second coordination shell

[Robert Gordon]

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 <mailto:eugenio_otal at shinshu-u.ac.jp>
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