On Thu, Oct 6, 2011 at 12:50 PM,
<ifeffit-request@millenia.cars.aps.anl.gov> wrote:
Send Ifeffit mailing list submissions to
ifeffit@millenia.cars.aps.anl.gov
To subscribe or unsubscribe via the World Wide Web, visit
http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
or, via email, send a message with subject or body 'help' to
ifeffit-request@millenia.cars.aps.anl.gov
You can reach the person managing the list at
ifeffit-owner@millenia.cars.aps.anl.gov
When replying, please edit your Subject line so it is more specific
than "Re: Contents of Ifeffit digest..."
Today's Topics:
1. Re: Energy shift (Dr. Dariusz A. Zaj?c)
2. Zinc Sulfide fitting (Soham Mukherjee)
----------------------------------------------------------------------
Message: 1
Date: Thu, 06 Oct 2011 08:45:05 +0200
From: "Dr. Dariusz A. Zaj?c" <kicaj@ifj.edu.pl>
To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] Energy shift
Message-ID: <4E8D4E71.2000309@ifj.edu.pl>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
Your attachment do not help in this case...
Do you know something more about sample? I suppose it is a thin layer.
Have you checked if you have no defects, vacancies, etc?
I suppose that you can follow instructions given in this post
http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2009-January/008522.html
but you can be also interested in this topic:
http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2009-June/004293.html
and especially in last posts.
you can also try this suggestion
http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2010-June/009471.html
In general - could you precise, what is k_{min} for your fit, and did
you use self consistent potential in calculations?
W dniu 11-10-06 02:28, JeongEunSuk pisze:
> Thank Dariuz and Bruce.
> TiO is deposited on Si substrate and PtO is fabricated on TiO2.
> I measered EXAFS with Pt L3 edge(11563eV) and The model is decided
> from FEFF8.0.
> PtO has only fist shell like attached files So I chose the simple
> model with octahedral structure (probe atom Pt, others O)
> When the EXAFS was fitted by feffit, the variables were three eo(Enot
> in Artemis, energy shift), do1(distance factor), sigo1(debye-waller
> factor).
> the results of fit is as following
> variable best fit value uncertainty initial guess
> eo = 19.283398 1.726426 0.000000
> do1 = -0.023227 0.009557 0.096000
> sigo1 = 0.003790 0.000583 0.003047
> r-factor: 11
> reduced-chi square: 95
>
> Energy shift by fit shows an amount of difference from Pt L3 edge. It
> is my problem.
> To reduce the energy shift, I tried to remove background carefully
> again and to change distance Pt-O.
> However the result was failed.
>
>
>
> ------------------------------------------------------------------------
> Date: Wed, 5 Oct 2011 08:24:16 +0200
> From: kicaj@ifj.edu.pl
> To: ifeffit@millenia.cars.aps.anl.gov
> Subject: Re: [Ifeffit] Energy shift
>
> Hi,
> could say more precise what kind of energy shift you are talking
> about? the position of the white line or the Enot in Artemis. How big
> it is? Which version of Feff do you use? What do you mean writing
> "removing background carefully"? Background in the EXAFS fit? Any
> pictures to illustrate problem are welcome
>
> W dniu 11-10-05 03:25, JeongEunSuk pisze:
>
> Hell all
> I have the study for PtO nanoparticles with EXAFS.
> When I fitted the data to model, I had a problem for energy shift.
> I thought that the energy shift obtained from fitting must be
> below White line. However it was over white line.
> Although I removed background carefully and changed bond length in
> model, the energy shift was still big.
> I want to know other factors which affect energy shift.
>
>
> _______________________________________________
> Ifeffit mailing list
> Ifeffit@millenia.cars.aps.anl.gov <mailto:Ifeffit@millenia.cars.aps.anl.gov>
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>
>
> _______________________________________________ Ifeffit mailing list
> Ifeffit@millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>
>
> _______________________________________________
> Ifeffit mailing list
> Ifeffit@millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20111006/907c019b/attachment-0001.htm>
------------------------------
Message: 2
Date: Thu, 6 Oct 2011 12:50:24 +0530
From: Soham Mukherjee <soham.chem@gmail.com>
To: ifeffit@millenia.cars.aps.anl.gov
Subject: [Ifeffit] Zinc Sulfide fitting
Message-ID:
<CAH3zd5wQrqtkkML+vk8DsEcTbYn63SDuzTh-gssinJpVP2tJfQ@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Zinc Sulfide exists largely in two phases, either the cubic zinc-blende
(F-43m) phase, or the hexagonal wurtzite (P63cm) phase.
The details of the NN distances are as follows :-
1. For cubic phase, the NN distances (Zinc to Sulfur bond lengths) are
2.3028 Angstroms each, 4 such bonds exist in a tetrahedral arrangement;
2. For hexagonal phase, there are 2 different NN distances (Zinc to Sulfur
bond lengths) 3 bonds having the length 2.3421 Angstroms each, and 1 axially
elongated bond of length 2.3465 Angstroms. So they differ only by 0.0044
Angstroms !
I am performing a first shell fit to Zinc Sulfide which exists in the
wurtzite phase (hexagonal_P63cm). However, I could fit it quite well taking
the cubic phase (Zinc blende_F-43m) as my starting model. The only thing is
that since bond distances are higher in a hexagonal phase than the cubic
phase, I end up with a considerable delr as I underestimated my starting
bond length value. Taking a wurtzite model involves defining two different
bond lengths (which differ only by 0.0044 Angstroms !), paths 1 and 2 in the
FEFF, whose sigma^2 values are quite similar. This gives unusually large
delr values and high sigma^2 for the longer axial bond, which looks
suspicious !
Do I really need to define the two bond distances separately of so close
values? Or taking a cubic phase will be sufficient? Please find the attached
project file (artemis.apj) where I have tried out some simulations with both
cubic and hexagonal models.
With best regards,
Soham.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20111006/67aeec95/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: artemis.apj
Type: application/octet-stream
Size: 199478 bytes
Desc: not available
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20111006/67aeec95/attachment.obj>
------------------------------
_______________________________________________
Ifeffit mailing list
Ifeffit@millenia.cars.aps.anl.gov
http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
End of Ifeffit Digest, Vol 104, Issue 4
***************************************