fitting

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Differences between fluorescence...

mohamed sobhy

13 May 2010 13 May '10

4:21 p.m.

Dear all I am trying to use artemis to do fitting to CeO2. But really I cant get the right way to do that. During the fitting, I am using amp as set and change in N degeneracy of the path. attached is the best fit i got but it still not good and the chi-square is 41.109065479 so can you suggest me what to do thanks Mohamed

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Frenkel, Anatoly

13 May 13 May

4:25 p.m.

There is a large number of articles explaining how to fit CeO2 including discussions why multi-electron excitatoins complicate the fit, and some of those authors (e.g., A. Soldatov, but also M. Benfatto) propose first principle methods that account for those. Some papers even show that ignoring those contributions may give a decent fit, but you should be aware of the multitudes of theoretical issues surrounding EXAFS modeling of this system before trying it on your own. Anatoly ________________________________ From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of mohamed sobhy Sent: Thu 5/13/2010 5:21 PM To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] fitting Dear all I am trying to use artemis to do fitting to CeO2. But really I cant get the right way to do that. During the fitting, I am using amp as set and change in N degeneracy of the path. attached is the best fit i got but it still not good and the chi-square is 41.109065479 so can you suggest me what to do thanks Mohamed

María Elena Montero Cabrera

4:34 p.m.

I don't know anything about CeO2, but...for me there is something wrong since the Athena fitting, because there are too many peaks below the main one, and specially below 1 A. Am I right or not? Maria Elena 2010/5/13 Frenkel, Anatoly

...

There is a large number of articles explaining how to fit CeO2 including discussions why multi-electron excitatoins complicate the fit, and some of those authors (e.g., A. Soldatov, but also M. Benfatto) propose first principle methods that account for those. Some papers even show that ignoring those contributions may give a decent fit, but you should be aware of the multitudes of theoretical issues surrounding EXAFS modeling of this system before trying it on your own.

Anatoly

________________________________

From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of mohamed sobhy Sent: Thu 5/13/2010 5:21 PM To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] fitting

Dear all I am trying to use artemis to do fitting to CeO2. But really I cant get the right way to do that. During the fitting, I am using amp as set and change in N degeneracy of the path. attached is the best fit i got but it still not good and the chi-square is 41.109065479 so can you suggest me what to do

thanks

Mohamed

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

-- María Elena Dra. María Elena Montero Cabrera Departamento de Medio Ambiente y Energía Centro de Investigación en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Compl. Ind. Chihuahua Chihuahua CP 31109, Chih. México Tel (614) 4391123

Frenkel, Anatoly

4:38 p.m.

Then what I wrote is an overkill... Anatoly ________________________________ From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of María Elena Montero Cabrera Sent: Thu 5/13/2010 5:34 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] fitting I don't know anything about CeO2, but...for me there is something wrong since the Athena fitting, because there are too many peaks below the main one, and specially below 1 A. Am I right or not? Maria Elena 2010/5/13 Frenkel, Anatoly There is a large number of articles explaining how to fit CeO2 including discussions why multi-electron excitatoins complicate the fit, and some of those authors (e.g., A. Soldatov, but also M. Benfatto) propose first principle methods that account for those. Some papers even show that ignoring those contributions may give a decent fit, but you should be aware of the multitudes of theoretical issues surrounding EXAFS modeling of this system before trying it on your own. Anatoly ________________________________ From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of mohamed sobhy Sent: Thu 5/13/2010 5:21 PM To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] fitting Dear all I am trying to use artemis to do fitting to CeO2. But really I cant get the right way to do that. During the fitting, I am using amp as set and change in N degeneracy of the path. attached is the best fit i got but it still not good and the chi-square is 41.109065479 so can you suggest me what to do thanks Mohamed _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit -- María Elena Dra. María Elena Montero Cabrera Departamento de Medio Ambiente y Energía Centro de Investigación en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Compl. Ind. Chihuahua Chihuahua CP 31109, Chih. México Tel (614) 4391123

Stefan Mangold

4:48 p.m.

Hello, to ideas coming into my mind without an look at your data: 1. Very noisy data ... (may produce to many peaks) 2. problems with the background correction regards Stefan Am 13.05.2010 um 23:34 schrieb María Elena Montero Cabrera:

...

I don't know anything about CeO2, but...for me there is something wrong since the Athena fitting, because there are too many peaks below the main one, and specially below 1 A. Am I right or not?

Maria Elena

2010/5/13 Frenkel, Anatoly There is a large number of articles explaining how to fit CeO2 including discussions why multi-electron excitatoins complicate the fit, and some of those authors (e.g., A. Soldatov, but also M. Benfatto) propose first principle methods that account for those. Some papers even show that ignoring those contributions may give a decent fit, but you should be aware of the multitudes of theoretical issues surrounding EXAFS modeling of this system before trying it on your own.

Anatoly

________________________________

From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of mohamed sobhy Sent: Thu 5/13/2010 5:21 PM To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] fitting

Dear all I am trying to use artemis to do fitting to CeO2. But really I cant get the right way to do that. During the fitting, I am using amp as set and change in N degeneracy of the path. attached is the best fit i got but it still not good and the chi-square is 41.109065479 so can you suggest me what to do

thanks

Mohamed

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

-- María Elena

Dra. María Elena Montero Cabrera Departamento de Medio Ambiente y Energía Centro de Investigación en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Compl. Ind. Chihuahua Chihuahua CP 31109, Chih. México Tel (614) 4391123 _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

-- Dr. Stefan Mangold Institut für Synchrotronstrahlung Forschungszentrum Karlsruhe Tel.: +49-7247-826073

shelly Kelly

6:10 p.m.

I agree. To see if the problem is at high k, just make three copies of the data and then ft it with larger values for kmax. That would indicate noise as the problem. You can do the same at low k by adjusting kmin. That would indicate a problem with the background. You can find examples of these methods in my book chapter. Send me an email and I'll send it to you. Tht Shelly -- Sent from my Palm Prē On May 13, 2010 4:53 PM, Stefan Mangold <stefan.mangold@iss.fzk.de> wrote: Hello, to ideas coming into my mind without an look at your data: 1. Very noisy data ... (may produce to many peaks)2. problems with the background correction regards Stefan Am 13.05.2010 um 23:34 schrieb María Elena Montero Cabrera:I don't know anything about CeO2, but...for me there is something wrong since the Athena fitting, because there are too many peaks below the main one, and specially below 1 A. Am I right or not? Maria Elena 2010/5/13 Frenkel, Anatoly <frenkel@bnl.gov> There is a large number of articles explaining how to fit CeO2 including discussions why multi-electron excitatoins complicate the fit, and some of those authors (e.g., A. Soldatov, but also M. Benfatto) propose first principle methods that account for those. Some papers even show that ignoring those contributions may give a decent fit, but you should be aware of the multitudes of theoretical issues surrounding EXAFS modeling of this system before trying it on your own. Anatoly ________________________________ From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of mohamed sobhy Sent: Thu 5/13/2010 5:21 PM To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] fitting Dear all I am trying to use artemis to do fitting to CeO2. But really I cant get the right way to do that. During the fitting, I am using amp as set and change in N degeneracy of the path. attached is the best fit i got but it still not good and the chi-square is 41.109065479 so can you suggest me what to do thanks Mohamed _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit -- María Elena Dra. María Elena Montero Cabrera Departamento de Medio Ambiente y Energía Centro de Investigación en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Compl. Ind. Chihuahua Chihuahua CP 31109, Chih. México Tel (614) 4391123 _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit -- Dr. Stefan Mangold Institut für Synchrotronstrahlung Forschungszentrum Karlsruhe Tel.: +49-7247-826073

Bruce Ravel

6:59 p.m.

On Thursday 13 May 2010, 05:21:02 pm, mohamed sobhy wrote:

...

Dear all I am trying to use artemis to do fitting to CeO2. But really I cant get the right way to do that. During the fitting, I am using amp as set and change in N degeneracy of the path. attached is the best fit i got but it still not good and the chi-square is 41.109065479 so can you suggest me what to do

Mohamed, I think you need to do some homework. Along with Shelly's suggestion, I suspect that you need to read up on the meaning of the Rbkg parameter in Athena. There is some discussion of this in the Athena manual. Shelly's book chapter is very useful. I suggest you also read up on what's been written about how to interpret chi- square. Look through the stuff at xafs.org. Matt, Shelly, and Scott -- as well as myself and others -- have written extensively about how to think about chi-square. It is not obvious just from looking at a picture that there is anything wrong with your fit. B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 My homepage: http://xafs.org/BruceRavel EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/

Iztok Arčon

14 May 14 May

1:59 a.m.

Dear Mohamed, There is an example of CeO2 EXAFS analysis, taking into account background problems, in the following paper: *J. Padežnik Gomilšek, I. Kozjek-Škofic, N. Bukovec, A. Kodre */X-ray absorption study of CeO2 and Ce/V mixed oxide thin films obtained by sol-gel deposition. /* *Thin solid films, vol. 446, issue 1, (2004) 117-123. regards Iztok Arcon mohamed sobhy wrote:

...

Dear all I am trying to use artemis to do fitting to CeO2. But really I cant get the right way to do that. During the fitting, I am using amp as set and change in N degeneracy of the path. attached is the best fit i got but it still not good and the chi-square is 41.109065479 so can you suggest me what to do

thanks

Mohamed

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-- Iztok Arcon University of Nova Gorica Vipavska 13, POB 301 5001 Nova Gorica, Slovenia tel: +386 5 331 5227 fax: +386 5 331 5240 e-mail: iztok.arcon@ung.si http://www.ung.si/~arcon http://www.ung.si/~arcon/xas

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Bruce Ravel
Frenkel, Anatoly
Iztok Arčon
María Elena Montero Cabrera
mohamed sobhy
shelly Kelly
Stefan Mangold

fitting

mohamed sobhy

Frenkel, Anatoly

María Elena Montero Cabrera

Frenkel, Anatoly

Stefan Mangold

shelly Kelly

Bruce Ravel

Iztok Arčon

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