[Ifeffit] Amplitude in Artemis

[Carlo Segre]

Shelly:

I took a look at Paul's data and this is what he was referring to.  If the 
first shell is fit with a single scatterer of oxygen, it gives about 13 
near neighbors.

Carlo

On Tue, 28 Feb 2006, Kelly, Shelly D. wrote:

> Hi Paul,
>
>
>
> How close are the distances for the 6 ligands?  It is usually not
> possible to fit a single peak in the EXAFS spectrum by 6 independent
> signals.  It sound like the distribution of distances for these 6
> ligands is incorrect.  I suggest that you try to fit just the first peak
> with one and then with two different shells with unknown coordination
> numbers and distances.  This will give you some more information about
> what the data indicate the structure is like.
>
>
>
> If you send me an artemis file, I'll take a peak at it.
>
>
>
> Shelly
>
> skelly at anl.gov
>
> ________________________________
>
> From: ifeffit-bounces at millenia.cars.aps.anl.gov
> [mailto:ifeffit-bounces at millenia.cars.aps.anl.gov] On Behalf Of Paul
> Sent: Monday, February 27, 2006 6:31 PM
> To: XAFS Analysis using Ifeffit
> Subject: Re: [Ifeffit] Amplitude in Artemis
>
>
>
> Hi Shelly
>
>
>
> Unfortunately the coordination number is 1 for all atoms present. I have
> the crystal structure of the complex, so I am currently including 6
> ligating atoms all at distances defined by the structure in the input
> file. It seems to be the first shell that is causing the problems, with
> a quickfit first shell artemis fit giving nominally 13 ligating species
> (which is of course absurd). So I believe something else must be the
> problem.
>
>
>
> Cheers
>
>
>
> Paul
>
> 	----- Original Message -----
>
> 	From: Kelly, Shelly D. <mailto:SKelly at anl.gov>
>
> 	To: XAFS Analysis using Ifeffit
> <mailto:ifeffit at millenia.cars.aps.anl.gov>
>
> 	Sent: Tuesday, February 28, 2006 12:55 AM
>
> 	Subject: RE: [Ifeffit] Amplitude in Artemis
>
>
>
> 	Hi Paul,
>
>
>
> 	It seems possible that one of the other amplitude terms is also
> incorrect.  Scott already mentioned the step height but what about the
> coordination number?  The amplitude of the model is given by
> coordination number * S02.  You mentioned that the S02 value was
> somewhere between 2 and 4.  What is the value for coordination number *
> S02?  If the coordination number is 1, then it is possible that the
> parameters are switched.  Maybe the coordination number should be
> between 2 and 4 and S02 should be around 1.
>
>
>
> 	HTH,
>
> 	Shelly
>
>
>
>
> ________________________________
>
>
> 	From: ifeffit-bounces at millenia.cars.aps.anl.gov
> [mailto:ifeffit-bounces at millenia.cars.aps.anl.gov] On Behalf Of Paul
> 	Sent: Sunday, February 26, 2006 6:52 PM
> 	To: ifeffit at millenia.cars.aps.anl.gov
> 	Subject: [Ifeffit] Amplitude in Artemis
>
>
>
> 	I have just started a PhD and have been given alot of EXAFS data
> to simulate but I don't know much about artemis. I have tried to fit the
> data for quite some time now, but can't get any kind of good fit unless
> the amplitude is above 1. Is there any way amp can be above 1 and
> rationally explained?
>
>
>
> 	Cheers,
>
>
>
> 	Paul
>
>
> ________________________________
>
>
> 	_______________________________________________
> 	Ifeffit mailing list
> 	Ifeffit at millenia.cars.aps.anl.gov
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>
>

-- 
Carlo U. Segre -- Professor of Physics
Associate Dean for Special Projects, Graduate College
Illinois Institute of Technology
Voice: 312.567.3498            Fax: 312.567.3494
Carlo.Segre at iit.edu    http://www.iit.edu/~segre