[Ifeffit] Mn3O4 EXAFS fitting

[Scott Calvin]

Hi Kug-Seung,

Fred has explained the basic issues with spinels well. For an example of how to handle them, you can see this article of mine:

http://journals.aps.org/prb/abstract/10.1103/PhysRevB.66.224405

If you don’t have access to the article, let me know, and I can email you a copy.

—Scott Calvin
Sarah Lawrence College

> On Jun 1, 2015, at 5:07 AM, fred.mosselmans at diamond.ac.uk wrote:
> 
> Dear Kug-Seung 
> 
> Your main initial problem is you didn't understand the structure of Mn3O4. It is a spinel with two Mn sites one octahedral and one tetrahedral. You need to consider both sites to have a chance of fitting, and set multiplication factors on the relative amps in the ratio. It has 1/3 tetrahedral sites and 2/3 octahedral. You need to do the feff calculation twice with each site as the core atom.
> In the attached project I have done this. You then end up with a lot of paths so to try to restrict the no of variables I have made several of sigma squared to be the same.  I am sure this model could be improved upon but  I wanted to show you how to get going in fitting the structure. In theory as the Mn tetrahedral site and octahedral sites are different oxidations states they might (should) have different E0s as well but with a limited data range this gets hard to test properly.
> 
> Best wishes
> Fred Mosselmans
> 
> 
> Message: 1
> Date: Mon, 01 Jun 2015 15:59:40 +0900
> From: ??? <lks3006 at postech.ac.kr>
> To: ifeffit at millenia.cars.aps.anl.gov
> Subject: [Ifeffit] Mn3O4 EXAFS fitting
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