[Ifeffit] How to keep enot, delr, and ss within acceptable limits

[JeongEunSuk]

Hi
I saw your figure. The second peak of Nanocrystal in wurtzite generally is week or not, because there is an amount of disorder in second shell.
The second peak in your fitting may make a problem.  
First, Fit your data in first shell with 4 nitrogen atoms, not with second shell. After that, you can fit second shell with 'set first shell varables'.
To fit second shell is not easy. when you fit second shell, check the number of second shell atoms. I think there are not 12 In around probe atom.
 



Date: Mon, 12 Jan 2009 15:30:52 +0700From: kaswat at gmail.comTo: ifeffit at millenia.cars.aps.anl.govSubject: Re: [Ifeffit] How to keep enot, delr, and ss within acceptable limits
Dear all,
 
I have the same problem with Hashem. 
 
My sample is nanocrystal Wurtzite InN (XRD and AFM results). I do the absorption experiment at In L3-edge at room temperature. After an data processing process, I get 2 broad peaks in FT. When i try to fitting a Wurtzite InN model to the EXAFS spectra for the first and second shells, I always get unacceptable parameters. First of all, I try to change my WZ InN model (changing lattice constant a and c, u-parameter) but it is inefficiently. How could I do?
 
This figure 1 shown a FT of In-L3 EXAFS spectra, the Blue line is my 2 broad peaks and red line is calculate with my WZ InN model which set all parameter to initial value (not guess any thing).
 
figure 1 >> http://nanotech.sytes.net/kaswat/01.emf
 
After I have read Bruce's mail ("If your sigma^2 parameter is negative, perhaps you have too much structural disorder in your model and the fit is compensating by inflating those paths with a negative sigma^2."). How do I construct a WZ InN model which have too many structural disorder.
 
P.S. I have read some papers, they have use model of nanocrystalline alloy which containing amorphous model. How to construct an amorphous model like they.-- Mr. Kittiphong Amnuyswat [kaswat]Post Graduate student College of KMITL NanotechnologyContact : kaswat at gmail.com, nakz_zz at hotmail.com [MSN Available]
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