[Ifeffit] Question about Artemis
Dear IFEFFIT-friends, I am working with Demeter version 0.9.26. In older versions of Artemis, I remember being able to load FEFF9 to produce the model for fitting, but I can't figure out how to do it in this version. I have only found how to write the Atoms results to be read by FEFF8. Is there a way to use the version of FEFF9 for this version of Artemis? Can anyone tell me how it's done or instead recommend where to get documentation on it? Thank you very much in advance Regards María Elena Dra. María Elena Montero Cabrera Centro de Investigación en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Complejo Industrial Chihuahua Chihuahua CP 31136, Chih. México Tel (614) 4391123 ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit
Re: [Ifeffit] ATOMS for XANES simulation by FEFF8.4
Thank you very much, Johan. I have another question, probably for Bruce: In the latest version of Artemis (before the release of Demeter) it was possible to edit preferences for running FEFF. I mean, when I acquired the FEFF version 8.4, I could tell Artemis to run this FEFF, instead of FEFF6. In the current version of Artemis may be it is, but I didn't find this possibility. Would somebody advice me in this task? Thanking in advance Maria Elena María Elena Dra. María Elena Montero Cabrera Centro de Investigación en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Compl. Ind. Chihuahua Chihuahua CP 31136, Chih. México Tel (614) 4391123 http://redtuls.org/ 2015-09-15 10:26 GMT-06:00 Johan Nilsson <johan.nils...@chalmers.se>: > Hello Maria, > > You can use the stand-alone Atoms application included in demeter to > prepare feff8 input files from crystallographic data, in the application > under the "atoms" tab there is a button called "export" and then you can > select feff8 as an output format. You should be able to do the same thing > with webatoms in your browser and get a similar result. In either case for > a XANES calculation you will probably edit the input file manually > afterwards to set the desired input parameters for the calculation. > > I believe that EXAFS fitting in Artemis can only be done with feff6 which > is included in demeter so you probably need to prepare a separate input > file for that without any input cards specific to later versions of feff. > > Best wishes, > Johan > > -- > *From:* ifeffit-boun...@millenia.cars.aps.anl.gov [ > ifeffit-boun...@millenia.cars.aps.anl.gov] on behalf of María Elena > Montero Cabrera [elena.mont...@cimav.edu.mx] > *Sent:* 13 September 2015 01:52 > *To:* XAFS Analysis using Ifeffit > *Subject:* [Ifeffit] ATOMS for XANES simulation by FEFF8.4 > > Dear all, > I am trying to "produce" a new feff.inp using the space group, the > asymmetric unit and related data of a compound, for simulating XANES by > using FEFF8.4. Long time ago I have used the program "WebAtoms" for > obtaining the file, and afterwards I used to edit it, as you have to > "uncomment" some lines and "comment" others to run FEFF for XANES. > However, in the "Artemis-Demeter" program you have ATOMS also, and Bruce > explicitly tells you that the old WebAtoms is not "supported". When I run > my data from my compound in Artemis the feff.inp file I have obtained > looks, at least for me, different from that I have expected for running > XANES in FEFF. > Please, tell me what I have to do. Should I use the old Atoms, or I have > to tell Atoms in Artemis that I want a "XANES" feff.inp? How can I do it? > Thanks a lot in advance > > María Elena > > Dra. María Elena Montero Cabrera > Centro de Investigación en Materiales Avanzados (CIMAV) > Miguel de Cervantes 120, Compl. Ind. Chihuahua > Chihuahua CP 31136, Chih. México > Tel (614) 4391123 > http://redtuls.org/ > > ___ > 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
Re: [Ifeffit] ATOMS for XANES simulation by FEFF8.4
Thank you, Bruce. No problems, I can wait. Regards Maria Elena María Elena Dra. María Elena Montero Cabrera Centro de Investigación en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Compl. Ind. Chihuahua Chihuahua CP 31136, Chih. México Tel (614) 4391123 http://redtuls.org/ 2015-09-16 9:33 GMT-06:00 Bruce Ravel <bra...@bnl.gov>: > On 09/16/2015 11:20 AM, María Elena Montero Cabrera wrote: > >> In the latest version of Artemis (before the release of Demeter) it was >> possible to edit preferences for running FEFF. I mean, when I acquired >> the FEFF version 8.4, I could tell Artemis to run this FEFF, instead of >> FEFF6. In the current version of Artemis may be it is, but I didn't find >> this possibility. Would somebody advice me in this task? >> > > Feff8 is poorly supported in the current version of Artemis. That said, > this has been discussed many times on the mailing list and can be found in > the archives. > > I am working towards transitioning Artemis to use feff85exafs ( > https://github.com/xraypy/feff85exafs), but that will take a few months. > > This is relevant to the feff6/feff8 discussion: > http://bruceravel.github.io/SCFtests/scf.html > > B > > > -- > Bruce Ravel bra...@bnl.gov > > National Institute of Standards and Technology > Synchrotron Science Group at NSLS-II > Building 535A > Upton NY, 11973 > > Homepage:http://bruceravel.github.io/home/ > Software:https://github.com/bruceravel > Demeter: http://bruceravel.github.io/demeter/ > > ___ > 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
Re: [Ifeffit] ATOMS for XANES simulation by FEFF8.4
Dear all, After reading again the FEFF8.4 Manual, I decided that using WebATOMS is a good option. If you have another suggestion, please let me know. Best regards María Elena Dra. María Elena Montero Cabrera Centro de Investigación en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Compl. Ind. Chihuahua Chihuahua CP 31136, Chih. México Tel (614) 4391123 http://redtuls.org/ 2015-09-12 17:52 GMT-06:00 María Elena Montero Cabrera < elena.mont...@cimav.edu.mx>: > Dear all, > I am trying to "produce" a new feff.inp using the space group, the > asymmetric unit and related data of a compound, for simulating XANES by > using FEFF8.4. Long time ago I have used the program "WebAtoms" for > obtaining the file, and afterwards I used to edit it, as you have to > "uncomment" some lines and "comment" others to run FEFF for XANES. > However, in the "Artemis-Demeter" program you have ATOMS also, and Bruce > explicitly tells you that the old WebAtoms is not "supported". When I run > my data from my compound in Artemis the feff.inp file I have obtained > looks, at least for me, different from that I have expected for running > XANES in FEFF. > Please, tell me what I have to do. Should I use the old Atoms, or I have > to tell Atoms in Artemis that I want a "XANES" feff.inp? How can I do it? > Thanks a lot in advance > > María Elena > > Dra. María Elena Montero Cabrera > Centro de Investigación en Materiales Avanzados (CIMAV) > Miguel de Cervantes 120, Compl. Ind. Chihuahua > Chihuahua CP 31136, Chih. México > Tel (614) 4391123 > http://redtuls.org/ > ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
[Ifeffit] ATOMS for XANES simulation by FEFF8.4
Dear all, I am trying to "produce" a new feff.inp using the space group, the asymmetric unit and related data of a compound, for simulating XANES by using FEFF8.4. Long time ago I have used the program "WebAtoms" for obtaining the file, and afterwards I used to edit it, as you have to "uncomment" some lines and "comment" others to run FEFF for XANES. However, in the "Artemis-Demeter" program you have ATOMS also, and Bruce explicitly tells you that the old WebAtoms is not "supported". When I run my data from my compound in Artemis the feff.inp file I have obtained looks, at least for me, different from that I have expected for running XANES in FEFF. Please, tell me what I have to do. Should I use the old Atoms, or I have to tell Atoms in Artemis that I want a "XANES" feff.inp? How can I do it? Thanks a lot in advance María Elena Dra. María Elena Montero Cabrera Centro de Investigación en Materiales Avanzados (CIMAV) Miguel de Cervantes 120, Compl. Ind. Chihuahua Chihuahua CP 31136, Chih. México Tel (614) 4391123 http://redtuls.org/ ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
Re: [Ifeffit] Linear Combination Fitting using ATHENA
Hi all! I am out of my place and I can not check it now, but I believe that in the database of XAFS (or something like that) there are some spectra of maghemites obtained by Lytle long time ago. Best regards Maria Elena Montero Cabrera El ago 13, 2013 3:38 a.m., Teck Kwang Choo teck.kwang.c...@monash.edu escribió: Hi all, @Drew Latta: I was wondering why the end members should be magnetite and maghemite. Is it because they are both of inverse-spinel structure, the difference only being that the latter has all Fe completely oxidized into Fe(III)? Would you be able to provide the standard spectra to me if that is the case? Thanks very much! Previously I have only thought of using hematite (alpha-Fe2O3) and FeO as end-members, both representing Fe(III) and Fe(II) respectively without giving much thought to the structure Fe takes. I also had my doubts using magnetite (Fe3O4) as a standard as it is a mixture of both Fe (II) and Fe (III). But thanks to the insights Drew has given, I now think I should take the Fe-coordination environment into account with the use of magnetite and maghemite as standards. @Alexandre and Matthew: I have obtained Mossbauer spectra of some of my samples but like Drew said, it is not straightforward at this point in time. Will see what I can do with the data I have! Thanks for all your responses! It is greatly appreciated! This forum has been more helpful than I thought! Teck Kwang On 13 August 2013 01:34, Matthew Marcus mamar...@lbl.gov wrote: While it's true that Mossbauer is the gold standard for Fe valence determination, access to the technique isn't all that common, and I don't know of any facility that can do it on a micro scale. Is there one? mam On 8/12/2013 7:01 AM, Alexandre dos Santos Anastacio wrote: Hello, maybe that fingerprinting technique would be Mossbauer spectroscopy. The Fe(II)/Fe(III) ratio comes easily and also there are lots of papers about Mg-ferrite, an example: 10.1109/TMAG.2009.2018880 http://dx.doi.org/10.1109/**TMAG.2009.2018880http://dx.doi.org/10.1109/TMAG.2009.2018880 Alexandre. __**_ Ifeffit mailing list ifef...@millenia.cars.aps.anl.**gov Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.**gov/mailman/listinfo/ifeffithttp://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit __**_ Ifeffit mailing list ifef...@millenia.cars.aps.anl.**gov Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.**gov/mailman/listinfo/ifeffithttp://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit -- Teck Kwang Choo PhD Student Department of Chemical Engineering Room 225, Building 36 Monash University Mobile No.: 04-11489904 ___ 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
Re: [Ifeffit] Ifeffit Digest, Vol 114, Issue 5
doing this and wasnt aware that i should lengthen my pre and post-edge for later on analysis. This will be good lesson for the future. So you would not recommend doing linear combination fitting? I was planning on trying it out.. But I wouldnt want to do it if with my pre- and post-edge range, I am bound to derive wrong conclusions from the data. Best, Marie ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit -- Message: 3 Date: Thu, 9 Aug 2012 00:21:14 -0400 From: Enyuan Hu bearcha...@gmail.com To: ifeffit ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] pre-edge centroid Message-ID: CAJud35NRYb67J7xLATPHPJGjEyvOK_gUKZur+dL9T30x8k= u...@mail.gmail.com Content-Type: text/plain; charset=iso-8859-1 Dear all, I was wondering if anyone could comment on how to get the centroid of pre-edge by fitting the pre-edge peak by pseudo-Voigt functions. I tried to do that in Athena, but it seemed that peaking fitting part is the relatively less developed function in the software. Any comment would be appreciated. Enyuan -- next part -- An HTML attachment was scrubbed... URL: http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20120809/3a09d07c/attachment-0001.htm -- Message: 4 Date: Thu, 09 Aug 2012 15:11:31 +0200 From: Dominik Samuelis d.samue...@fkf.mpg.de To: XAFS Analysis using Ifeffit ifeffit@millenia.cars.aps.anl.gov Subject: Re: [Ifeffit] pre-edge centroid Message-ID: 5023b703.6020...@fkf.mpg.de Content-Type: text/plain; charset=iso-8859-1; Format=flowed Dear Enyuan, in my experience, peak fitting works very well with Athena. Try not to fit only the prepeak, but maybe include an arctan describing the edge (see attached pdf, the fit was made using athena). This makes isolating the prepeak much more reliable. Best regards, Dominik On 09.08.2012 06:21, Enyuan Hu wrote: Dear all, I was wondering if anyone could comment on how to get the centroid of pre-edge by fitting the pre-edge peak by pseudo-Voigt functions. I tried to do that in Athena, but it seemed that peaking fitting part is the relatively less developed function in the software. Any comment would be appreciated. Enyuan ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit -- Dr. Dominik Samuelis d.samue...@fkf.mpg.de Max-Planck-Institut f?r Festk?rperforschung Max Planck Institute for Solid State Research Heisenbergstr. 1 70569 Stuttgart Germany Phone +49-711-689-1769 Fax +49-711-689-1722 Web http://www.fkf.mpg.de/maier/ -- next part -- A non-text attachment was scrubbed... Name: prepeak_fit.pdf Type: application/pdf Size: 108409 bytes Desc: not available URL: http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20120809/83335ed8/attachment.pdf -- next part -- A non-text attachment was scrubbed... Name: smime.p7s Type: application/pkcs7-signature Size: 4534 bytes Desc: S/MIME Cryptographic Signature URL: http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20120809/83335ed8/attachment.p7s -- ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit End of Ifeffit Digest, Vol 114, Issue 5 *** ___ 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 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
Re: [Ifeffit] how to obtain average vacancy files?
Dear friends from the Ifeffit list, specially Sebastiano and Bruce, Thank you very much for your advices. Here I am giving you a better explanation of the physical problem we are facing, and then I´ll give the approach we will try to follow now. We are working on a 50-50 Cr-Fe maghemite, which structure is known by high resolution XRD and Rietveld method. The synthesis of such a maghemite is difficult and some magnetic properties are being measured. We know, also, that pure Fe maghemite structure at T=10 K has ordered vacancies. We are trying to verify by XAFS if the local environment of Cr or Fe absorbers reflects ordered vacancies. With the aid of crystallographic codes we modeled the various vacancy configurations, including the one corresponding to the ordered Fe maghemite structure. By the Rietveld analysis and by the XANES Cr spectrum we know that Cr occupies only octahedral sites. We have tried to fit with Artemis the experimental Cr and Fe EXAFS spectra, comparing them with one model of the ordered vacancies structure. The results are not the best, and then we “suspect” that the model of ordered vacancies is not the good one. As I have written before, our idea was to obtain “average vacancies” FEFF files and to work with the fully occupied magnetite structure, but with some kind of “gray” atoms. These gray atoms would be the average of vacancies and Cr or Fe atoms in octahedral sites. After your comments, it seems too difficult to obtain the corresponding FEFF functions. As a way for testing the disordered model, we are now working on the much easier problem of fitting the magnetite structure to our EXAFS spectra and to obtain the corresponding interatomic distances and amplitudes. We hope their interpretation will be also easier than before. Thanks a lot again for your attention. Best regards Maria Elena 2012/5/31 elena.mont...@cimav.edu.mx Dear friends: Thank you very much for your kind answers. Believe me, now I am in a hurry, and I hope this evening I'll answer with more details. Regards Maria Elena Enviado desde mi oficina móvil BlackBerry® de Telcel -Original Message- From: Bruce Ravel bra...@bnl.gov Sender: ifeffit-boun...@millenia.cars.aps.anl.gov Date: Thu, 31 May 2012 09:33:29 To: XAFS Analysis using Ifeffitifeffit@millenia.cars.aps.anl.gov Reply-To: XAFS Analysis using Ifeffit ifeffit@millenia.cars.aps.anl.gov Subject: Re: [Ifeffit] how to obtain average vacancy files? On Tuesday, May 29, 2012 10:31:43 PM María Elena Montero Cabrera wrote: Dear friends, I am trying to fit with Artemis, not very successfully, a maghemite structure. The main difficulty seems to be the vacancies in the structure. My idea, following a recently given Bruce’s advice to a person in this list, is to obtain “average vacancies” FEFF files and to work with the fully occupied magnetite structure. I wanted to obtain each file for a given vacancy configuration in the first coordination sphere and then to multiply the obtained functions by the weight of each configuration and summ them all. I had the hope of doing this by using the feff00nn.dat files that I have used when working with SixPack, some years ago. Surprisingly, I couldn’t find the Artemis’ corresponding feff00nn.dat files at any folder. What can I do? There are two questions here. I'll answer the second one first. It would be reasonable to say that the whole point of Artemis is to free the user from having to manage the feff.dat files. They get stashed in an out-of-the-way location so that the user can focus on creating a fitting model rather than keep track of many (dozens, hundreds,...) of little text files. You are not very clear about what, exactly, your confusion is in terms of the vacancy thing. So I can only make a guess. In general, vacancies are hard to model in Feff. In any case, it is may be imporssible to do a good job of modeling a vacancy with a /single/ Feff calculation. The reason is the same as the reason as for dopants -- Feff requires that every point in the cluster be occupied by only one kind of thing -- i.e. an atom or nothing. In general, you cannot know how to distribute the vacancy in the small cluster represented in the feff.inp file. The word vacancy makes much more sense in a crystallographic context where the structure is averaged over 10^23 atoms. In an EXAFS context, you have to figure out how to model both of the main effects of missing atom: * Reduction in coordination * Change in the distances to other neighboring atoms due to relaxation around the missing atom. I think that, if you spend some time reading papers by the folks who answer questions around here, you will find that the prefered approach to solving a problem involving vacancies is to run Feff on the native structure, then to parameterize the fit in such a way that models the coordinaton reduction and the changes in bond lengths. That is, I
Re: [Ifeffit] UO2 thin films on STO
Dear Mohamed, I think you will have some kind of over or self -absorption from the substrate, specially in geometries other than grazing incidence. I have performed that kind of experiments in fluorescence and in transmission. The result was that the absorption coefficient signal I was interested in, really was of 2nd or 3rd order of magnitud less that the tail of absorption of the substrate. I would not do that again. Maybe somebody has better experience. Regards Maria Elena 2010/11/16 mohamed sobhy bakhshwan1...@yahoo.com Dear All I would like to grow UO2 thin films on STO (SrTiO3) substrate but I found that Sr K-edge 16105 and U L3-edge is 17166. Do you think there will be any interference? Best, 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 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
Re: [Ifeffit] something is wrong with Ruthenium-Oxygen bond amplitudes
Thanks a lot, Wayne! I'll try to see spectra again with SixPack, which is close to SSRL data collection. I keep in touch. Best regards Maria Elena 2010/11/5 Wayne W Lukens Jr wwluk...@lbl.gov Hi Maria Elena, Your RuO2 spectrum does not look right to me. Here is a spectrum that I obtained on 11-2 in transmission. The sample is RuO2 powder brushed onto tape (16 layers of tape). Feff 7 fits the data well (amp is 1.1 for the oxygen shell if I allow it to vary). I think you my have either a sample or data collection issue. Since you have a good XRD, I would suspect the latter. For what it's worth, I have had problems with Ru metal and Feff and had to reduce amp to around 0.7 (if I remember correctly) to get a good fit. Sincerely, Wayne 2010/11/5 María Elena Montero Cabrera elena.mont...@cimav.edu.mx Hi Scott! Thanks a lot for your interest. The physical form was powder, and they were measured by transmission and fluorescence. We have tried firstly the fitting of fluorescence spectra, but we have obtained that low amplitude values. So I have though we have autoabsorption, and decided to do the fitting of transmission spectra. They are not exactly the same, close to the edge fluorescence spectra have lower mu(E). I remember that Sam Webb told me that the K edge jump was good in the absorption spectra, after calculating the thickness with Hephaestus. In that fitting we have obtained the same wrong values. Then we decided to do the fitting of RuO2, and we have obtained again the low amplitudes. Now I don't know what to do. Regards Maria Elena 2010/11/5 Scott Calvin dr.scott.cal...@gmail.com Hi Maria, What was the physical form of the samples (powder, thin film, etc.) and how were they measured (transmission, fluorescence, ...)? Sometimes this kind of thing can stem from sample/beamline/data effects. --Scott Calvin Sarah Lawrence College On Nov 5, 2010, at 5:50 PM, María Elena Montero Cabrera wrote: Hello friends, Hopping someone could help us. We are having some problems in fitting Ru K-edge in a Ruthenium-cuprate sample on Artemis, with path functions obtained using FEFF 8.4, where we got amplitude values of less than 0.50 for Ru-O first shells. We think this value probably is wrong, although there are some publications where some oxygen deficiency is studied and recorded as true. The ATOMS input data was found to be ok due to the Rietveld analysis results told us these are good. The reason we think we may be wrong with something during the fitting appeared because we tried to fit our reference sample of RuO2 (measured under same conditions as the experiment of Ru-Cu at SSRL) and we came to the same results, even worst, of amplitude lower than 0.40. We are attaching the Artemis files so you can take a look on it and give us some light to continue with our analysis. Thanking in advance, take care ___ 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 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 ___ 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 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
[Ifeffit] two measurements of the same compound in different beam-lines
Hi all! I have performed two independent XAFS measurements of Cr K-edge of the same Fe-Cr sample at two different beam-lines at SSRL. I have obtained the Fe-K edge data only once. The quality of data are different in each measurement. However, I cannot average spectra from different Cr-K measurements, and I don't know if I could take somehow advantage from having almost twice the information for the Cr- K adge, or I have to use only the better quality data and discard the other. What do you advice? If I can use both measurements, how can I do the fitting in Artemis? Thank you very much and all take care -- 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
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 fren...@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-boun...@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
[Ifeffit] asking for model compound data
Hello to all! I have looked to Matt Newville's data for model compounds, and I have not found those for gamma-Fe2O3, so called maghemite. Carlo Segre has provided me those from Litle Library, I thank very much his kindness. He has suggested me to obtain this way newer data. Would any of you provide me that, please? Thanking in advance -- 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
[Ifeffit] fitting simultaneously two different K-edges
Dear friends, Sam Webb, Bruce Ravel or any other, I have XAFS measurements, performed at SSRL at room temperature, of three compounds. All compounds have multielemental character and I have K-edge XAFS of two elements in each compound. It is desirable to make IFEFFIT fitting of both edges simultaneously. In all cases random solution of competing elements is assumed, but there are ferroelectricity, superconductivity or magnetic behaviors that are desirable to be explained. In each case, XAFS would confirm or reject the random character of the solution. I am not such an expert for resolving by myself how to fit together two edges using Artemis software. I'll present each case in the following: 1. rutheno-cuprate (Ru1-xNbx)Sr2Eu1.4 Ce0.6Cu2O10+δ compounds series was studied in both Ru and Nb K-edges. Changes in interatomic distances that could be obtained by EXAFS would tell something about oxygen octahedra around Ru and Nb. 2. g-Fe1-xCrxO3 maghemite for x=0.25, 0.5 and 0.75 was investigated by XAFS in both Fe and Cr K-edges. Possible distortion of oxygen octahedra around both Fe(III) and Cr(III) cations would tell something about not confirmed ferroelectricity. 3. LaFeNiTiO3 has been confirmed to display magnetic behavior and was studied by its Fe and Ti K-edges. Interatomic distances that could be obtained by EXAFS are interesting for checking possible preferential occupation of sites by Fe or Ti atoms. Would any of you, please, suggest how to use Artemis or Sixpack for solving these problems? Sincerely yours -- 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
