Re: [Ifeffit] Linear Combination Fitting using ATHENA
Hello again. Just want your opinion on a thought that I have. Due to the absence of Mg-ferrite (MgFe2O4) K-edge XANES spectrum, I have decided to do my Fe(II)/Fe(III) quantification with only maghemite and magnetite as end-member standards. Because Fe in MgFe2O4 exists entirely as Fe(III) and its structure is the same as both magnetite and maghemite (inverse-spinel structure with Fe (III) occupying both tetrahedral and octahedral sites), I am inferring that its K-edge XANES spectrum would be similar to that of maghemite. I am planning to take the quantified fraction of maghemite as a sum of the contributions of maghemite and Mg-ferrite. For instance, from Linear Combination Fitting: Fraction of Magnetite=0.05, Fraction of Maghemite = 0.95; Due to absence of Mg-ferrite spectrum, i will be taking (Fraction of Maghemite) + (Fraction of Mg-ferrite)= 0.95 What are your thoughts on this? Kind regards. Teck Kwang On 14 August 2013 18:46, Matthew Marcus mamar...@lbl.gov wrote: ** Yup. That's consistent. That sort of thing is why every XANES paper should state clearly the basis of the energy calibration. With Newville's database, you can often figure that out yourself because many of the spectra were done with a reference foil. mam - Original Message - *From:* Teck Kwang Choo teck.kwang.c...@monash.edu *To:* XAFS Analysis using Ifeffit ifeffit@millenia.cars.aps.anl.gov *Sent:* Wednesday, August 14, 2013 1:07 AM *Subject:* Re: [Ifeffit] Linear Combination Fitting using ATHENA Yes Matthew, I used 7112 eV for my Fe K-edge calibration. I am guessing that is the reason a ~+1 eV shift in your maghemite spectrum is required is required to fit mine. Both pre-edge features match in the sense that they are roughly bound by the same energy values. On 14 August 2013 17:30, Matthew Marcus mamar...@lbl.gov wrote: ** That depends on the way you did your calibration. If it really matches, including the pre-edge features, with a 1eV shift, then that's what you probably have. Did you take into account my calibration, which puts the Fe K-edge at 7110.75eV? Some people use other values like 7112eV. mam - Original Message - *From:* Teck Kwang Choo teck.kwang.c...@monash.edu *To:* XAFS Analysis using Ifeffit ifeffit@millenia.cars.aps.anl.gov *Sent:* Tuesday, August 13, 2013 9:20 PM *Subject:* Re: [Ifeffit] Linear Combination Fitting using ATHENA Also Matthew, I have found that my sample spectrum is an almost exact replica of the maghemite spectrum, the only differences being the absorbance height of the edge-peak (highest peak), which is ok but more importantly I have found that there is a +1eV shift of my spectrum relative to the maghemite one, probably due to slight differences in beamline. Do you think it is alright to make a +1 eV shift to the maghemite spectrum (or -1eV shift to my sample spectrum)? Thanks. Kind regards. Teck Kwang On 14 August 2013 10:07, Teck Kwang Choo teck.kwang.c...@monash.eduwrote: Thanks Matthew for the spectra. Is it correct to use the spectra that was taken in transmission mode (the one you did) to fit those taken in fluorescence mode (my case)? Teck Kwang On 14 August 2013 01:37, Matthew Marcus mamar...@lbl.gov wrote: Here are reference spectra. The calibration is defined with the Fe metal edge at 7110.75eV. The maghemite spectrum has been corrected for mild overabsorption by reference to magnetite, which is very similar. The magnetite is synthetic Fe3O4 from Aldrich, and done in TEY, so no overabsorption. The maghemite is from oxidation of Fe oxide nanoparticles and has been verified by XRD and comparison with the ETH group's maghemite spectrum. mam On 8/13/2013 1:33 AM, Teck Kwang Choo wrote: 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
Re: [Ifeffit] Linear Combination Fitting using ATHENA
Yes Matthew, I used 7112 eV for my Fe K-edge calibration. I am guessing that is the reason a ~+1 eV shift in your maghemite spectrum is required is required to fit mine. Both pre-edge features match in the sense that they are roughly bound by the same energy values. On 14 August 2013 17:30, Matthew Marcus mamar...@lbl.gov wrote: ** That depends on the way you did your calibration. If it really matches, including the pre-edge features, with a 1eV shift, then that's what you probably have. Did you take into account my calibration, which puts the Fe K-edge at 7110.75eV? Some people use other values like 7112eV. mam - Original Message - *From:* Teck Kwang Choo teck.kwang.c...@monash.edu *To:* XAFS Analysis using Ifeffit ifeffit@millenia.cars.aps.anl.gov *Sent:* Tuesday, August 13, 2013 9:20 PM *Subject:* Re: [Ifeffit] Linear Combination Fitting using ATHENA Also Matthew, I have found that my sample spectrum is an almost exact replica of the maghemite spectrum, the only differences being the absorbance height of the edge-peak (highest peak), which is ok but more importantly I have found that there is a +1eV shift of my spectrum relative to the maghemite one, probably due to slight differences in beamline. Do you think it is alright to make a +1 eV shift to the maghemite spectrum (or -1eV shift to my sample spectrum)? Thanks. Kind regards. Teck Kwang On 14 August 2013 10:07, Teck Kwang Choo teck.kwang.c...@monash.eduwrote: Thanks Matthew for the spectra. Is it correct to use the spectra that was taken in transmission mode (the one you did) to fit those taken in fluorescence mode (my case)? Teck Kwang On 14 August 2013 01:37, Matthew Marcus mamar...@lbl.gov wrote: Here are reference spectra. The calibration is defined with the Fe metal edge at 7110.75eV. The maghemite spectrum has been corrected for mild overabsorption by reference to magnetite, which is very similar. The magnetite is synthetic Fe3O4 from Aldrich, and done in TEY, so no overabsorption. The maghemite is from oxidation of Fe oxide nanoparticles and has been verified by XRD and comparison with the ETH group's maghemite spectrum. mam On 8/13/2013 1:33 AM, Teck Kwang Choo wrote: 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 mailto: 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.2009.2018880 http://dx.doi.org/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 mailto: ifef...@millenia.cars.**aps.anl.gov Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl._**_gov/mailman/listinfo/ifeffit 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 mailto: ifef...@millenia.cars.**aps.anl.gov Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl._**_gov/mailman/listinfo/ifeffit http://millenia.cars.aps.anl.**gov/mailman/listinfo/ifeffithttp
Re: [Ifeffit] Linear Combination Fitting using ATHENA
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
Re: [Ifeffit] Linear Combination Fitting using ATHENA
Here are reference spectra. The calibration is defined with the Fe metal edge at 7110.75eV. The maghemite spectrum has been corrected for mild overabsorption by reference to magnetite, which is very similar. The magnetite is synthetic Fe3O4 from Aldrich, and done in TEY, so no overabsorption. The maghemite is from oxidation of Fe oxide nanoparticles and has been verified by XRD and comparison with the ETH group's maghemite spectrum. mam On 8/13/2013 1:33 AM, Teck Kwang Choo wrote: 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 mailto: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.2009.2018880 http://dx.doi.org/10.1109/TMAG.2009.2018880 Alexandre. _ Ifeffit mailing list ifef...@millenia.cars.aps.anl.__gov mailto:Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.__gov/mailman/listinfo/ifeffit http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit _ Ifeffit mailing list ifef...@millenia.cars.aps.anl.__gov mailto:Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.__gov/mailman/listinfo/ifeffit http://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 #%Name: Maghemite nano powder #%Empirical formula: gamma-Fe3+2O3 /Webmineral #%Mineral group: oxides #%Xtal system: cubic #%Edge: K #%Sample prep: powder on Kapton tape #%Beamline: ALS 10.3.2, HxV slits = 200x20 um #%Det: I0=N2, Fluorescence mode (Ge solid state 7elts) #%Ref/notes: Mineralogical Research Company, San Jose, CA-USA. XRD confirmed. #%Temp: Room temp (28C) #%Timedate: 6:20 AM 7/3/2007 #%Provider: Matthew A. Marcus, Sirine Fakra. #% 7.0100066E+3 1.3008636E-3 7.0150081E+3 1.2676025E-3 7.0200096E+3 1.4012953E-3 7.0250111E+3 1.3687201E-3 7.0300126E+3 1.4827145E-3 7.0350141E+3 1.5567103E-3 7.0400156E+3 1.6321360E-3 7.0450172E+3 1.8282378E-3 7.0500187E+3 1.8787587E-3 7.0550202E+3 2.0697013E-3 7.0600217E+3 2.1766526E-3 7.0650232E+3 2.3976456E-3 7.0700247E+3 2.8091858E-3 7.0750262E+3 3.1121079E-3 7.0800277E+3 3.7051882E-3 7.0850292E+3 4.2254896E-3 7.0900307E+3 5.0080461E-3 7.0950323E+3 6.3616899E-3 7.1000338E+3 8.1449022E-3 7.1005339E+3 8.3578735E-3 7.1010341E+3 8.5095725E-3 7.1015342E+3 8.6762463E-3 7.1020344E+3 9.0579738E-3 7.1025345E+3 9.2831028E-3 7.1030347E+3 9.6193633E-3 7.1035348E+3 9.8628340E-3 7.1040350E+3 1.0180513E-2 7.1045351E+3 1.0386116E-2 7.1050353E+3 1.1052578E-2 7.1055355E+3 1.1529281E-2 7.1060356E+3 1.2050395E-2 7.1065358E+3 1.2378185E-2 7.1070359E+3 1.3171965E-2 7.1075361E+3 1.3657637E-2 7.1080362E+3 1.4476360E-2 7.1085364E+3 1.5504986E-2 7.1090365E+3 1.6594136E-2 7.1095367E+3 1.8050181E-2 7.1100368E+3 1.9940670E-2 7.1105370E+3 2.2958282E-2 7.1110371E+3 2.7349793E-2 7.1115373E+3 3.5642680E-2 7.1120374E+3 5.0382320E-2 7.1125376E+3 7.0824214E-2 7.1130377E+3 9.2282370E-2 7.1135379E+3 9.5804412E-2 7.1140380E+3 8.5603494E-2
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] Linear Combination Fitting using ATHENA
Also Matthew, I have found that my sample spectrum is an almost exact replica of the maghemite spectrum, the only differences being the absorbance height of the edge-peak (highest peak), which is ok but more importantly I have found that there is a +1eV shift of my spectrum relative to the maghemite one, probably due to slight differences in beamline. Do you think it is alright to make a +1 eV shift to the maghemite spectrum (or -1eV shift to my sample spectrum)? Thanks. Kind regards. Teck Kwang On 14 August 2013 10:07, Teck Kwang Choo teck.kwang.c...@monash.edu wrote: Thanks Matthew for the spectra. Is it correct to use the spectra that was taken in transmission mode (the one you did) to fit those taken in fluorescence mode (my case)? Teck Kwang On 14 August 2013 01:37, Matthew Marcus mamar...@lbl.gov wrote: Here are reference spectra. The calibration is defined with the Fe metal edge at 7110.75eV. The maghemite spectrum has been corrected for mild overabsorption by reference to magnetite, which is very similar. The magnetite is synthetic Fe3O4 from Aldrich, and done in TEY, so no overabsorption. The maghemite is from oxidation of Fe oxide nanoparticles and has been verified by XRD and comparison with the ETH group's maghemite spectrum. mam On 8/13/2013 1:33 AM, Teck Kwang Choo wrote: 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 mailto: 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.2009.2018880 http://dx.doi.org/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 mailto: ifef...@millenia.cars.**aps.anl.gov Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl._**_gov/mailman/listinfo/ifeffit 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 mailto:ifef...@millenia.cars. **aps.anl.gov Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl._**_gov/mailman/listinfo/ifeffit 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 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 Ifeffit@millenia.cars.aps.anl.gov http://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 -- Teck Kwang Choo PhD Student Department of Chemical Engineering Room 225, Building 36 Monash University Mobile No.: 04-11489904
Re: [Ifeffit] Linear Combination Fitting using ATHENA
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.2009.2018880 Alexandre. ___ 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
I would say that the Mossbauer isn't always quite straight forward, especially if the OP is working with nanoparticles. You have to find the right temperature where superparamagnetism is gone but the Verwey transition hasn't occurred to reliably fit the resulting Mossbauer spectra. (I'll assume from ignorance that that Mg-ferrites have Verwey transitions.) I would think the two best end-members for the XAS LC fits are possibly magnetite (fully stoichiometric: Fe2+/Fe3+ = 0.5) and either maghemite (gamma-Fe2O3) or the fully oxidized Mg-ferrite. Which Fe2O3 are you using Teck Kwang Choo? If you are using the alpha-form (hematite) then I would suspect you might not get very good fits as the structural difference between maghemite and hematite significantly influence their XANES spectra. I've had good success finding Fe2+/Fe3+ ratios in partially oxidized magnetites by using magnetite and maghemite as end-members in LC fits. So I think you should have reasonable success for the Mg-ferrites using the right end-members. Contact me in person below, if you are interested in magnetite/maghemite standard spectra. Best, Drew Latta --- Drew E. Latta, Ph.D. Postdoctoral Associate Molecular Environmental Science Group Biosciences Division Argonne National Laboratory Building 203, Room E-105 9700 South Cass Avenue Argonne, IL 60439 Phone: 1-630-252-3985 dla...@anl.govmailto:dla...@anl.gov http://www.mesg.anl.gov --- From: ifeffit-boun...@millenia.cars.aps.anl.gov [mailto:ifeffit-boun...@millenia.cars.aps.anl.gov] On Behalf Of Alexandre dos Santos Anastacio Sent: Monday, August 12, 2013 9:01 AM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] Linear Combination Fitting using ATHENA 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.2009.2018880http://dx.doi.org/10.1109/TMAG.2009.2018880 Alexandre. ___ 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
The database: http://cars.uchicago.edu/~newville/ModelLib/search.html does not seem to have Ferrite. The matrix of my sample is largely Mg-ferrite where Fe is in the form of Fe (III). If you anyone has the spectra for Mg-ferrite, would it be possible to provide it to me? Otherwise, I do not think my sample spectra would be useable at all! Thanks and kind regards. On 10 August 2013 02:21, Matthew Marcus mamar...@lbl.gov wrote: I would guess that you need better standards. In particular, FeO is not your typical Fe(II) mineral or oxide. What is the system you're working on? I have an extensive collection of Fe XANES reference spectra, including a number of Fe(II) species. LCF gives you the fraction of Fe atoms included in the sample. For example, suppose you had a sample which was genuinely a mix representable as FeO.Fe2O3. Then, LCF would properly report 2/3 Fe2O3 + 1/3 FeO because 2/3 of the Fe atoms are in the Fe2O3 fraction. mam On 8/8/2013 8:37 PM, Teck Kwang Choo wrote: Hello, I have been using ATHENA to perform Linear Combination Fitting (LCF) on my XANES spectrum to quantify the amounts of Fe (II) and Fe (III) in my samples using only FeO and Fe2O3 as standards. The results showed a majority of Fe (II), which is contrary to what was expected. This made me wonder if the LCF results from XANES is a molar percentage (mol %) or weight percentage (wt%). Could anyone enlighten me on this matter? Thanks! -- Teck Kwang Choo PhD Student Department of Chemical Engineering Room 225, Building 36 Monash University Mobile No.: 04-11489904 __**_ 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
Re: [Ifeffit] Linear Combination Fitting using ATHENA
That's magnetite unfortunately! On 12 August 2013 14:02, Scott Calvin scal...@sarahlawrence.edu wrote: Yes it does, Teck Kwang: http://millenia.cars.aps.anl.gov/cgi-bin/newville/Model-Search.cgi/ModelData/fe3o4_rt01_mar02.xmu --Scott Calvin Sarah Lawrence College On Aug 11, 2013, at 11:12 PM, Teck Kwang Choo teck.kwang.c...@monash.edu mailto:teck.kwang.c...@monash.edu wrote: The database: http://cars.uchicago.edu/~newville/ModelLib/search.html http://cars.uchicago.edu/%7Enewville/ModelLib/search.html does not seem to have Ferrite. The matrix of my sample is largely Mg-ferrite where Fe is in the form of Fe (III). If you anyone has the spectra for Mg-ferrite, would it be possible to provide it to me? Otherwise, I do not think my sample spectra would be useable at all! Thanks and kind regards. On 10 August 2013 02:21, Matthew Marcus mamar...@lbl.govmailto: mamar...@lbl.gov wrote: I would guess that you need better standards. In particular, FeO is not your typical Fe(II) mineral or oxide. What is the system you're working on? I have an extensive collection of Fe XANES reference spectra, including a number of Fe(II) species. LCF gives you the fraction of Fe atoms included in the sample. For example, suppose you had a sample which was genuinely a mix representable as FeO.Fe2O3. Then, LCF would properly report 2/3 Fe2O3 + 1/3 FeO because 2/3 of the Fe atoms are in the Fe2O3 fraction. mam On 8/8/2013 8:37 PM, Teck Kwang Choo wrote: Hello, I have been using ATHENA to perform Linear Combination Fitting (LCF) on my XANES spectrum to quantify the amounts of Fe (II) and Fe (III) in my samples using only FeO and Fe2O3 as standards. The results showed a majority of Fe (II), which is contrary to what was expected. This made me wonder if the LCF results from XANES is a molar percentage (mol %) or weight percentage (wt%). Could anyone enlighten me on this matter? Thanks! -- 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.govmailto:Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.govmailto:Ifeffit@millenia.cars.aps.anl.gov http://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.govmailto: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 -- 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
Re: [Ifeffit] Linear Combination Fitting using ATHENA
Dear Teck Kwang Choo, it is the ratio of the number of (in your case) iron atoms. This ratio has no unit. You will therefore get the same number if you calculate molar % ratio or weight % (Except you consider the weight of the missing electron in Fe3+... :-). Now, if you weigh your standards and want to calculate the number of Fe atoms you have to consider the weight of the oxygen. That means, the ratio you get from LCF fitting of your XAS spectra is NOT the ratio between mol of FeO and Fe2O3, but mol FeII+ to mol FeIII+! However, if necessary or usefull you can always calculate the latter from the FeII/FeIII ratio using the molar weights. So, as a chemist I would say, stay consequently with the molar ratio and you are on the safe side. You can always multiply the number of mol with the molar weight, but you would only make things more complicated and end up with the same ratio or, after multiplying with 100, percentage. Concerning the deviation between your result and your expectation: I would be more nervous about the choice of reference substances. If you only use FeO and Fe2O3 your result is only correct if your sample contains no other Fe component than these two. If it contains significant amounts of any other Fe component (even other oxides) you would better not draw any important conclusions from the result of your analysis. Best regards Edmund Welter On 09.08.2013 05:37, Teck Kwang Choo wrote: Hello, I have been using ATHENA to perform Linear Combination Fitting (LCF) on my XANES spectrum to quantify the amounts of Fe (II) and Fe (III) in my samples using only FeO and Fe2O3 as standards. The results showed a majority of Fe (II), which is contrary to what was expected. This made me wonder if the LCF results from XANES is a molar percentage (mol %) or weight percentage (wt%). Could anyone enlighten me on this matter? Thanks! -- 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] Linear Combination Fitting using ATHENA
Thanks for your reply Edmund. I agree with you that I might have not chosen the right standards for my sample. In fact, XRD analysis have confirmed that Ferrite is the main form of Fe in my sample but I did not have any ferrite standards during XANES analysis. Was wondering if you happen to have any Ferrite XANES spectra by any chance? Thanks and kind regards. Teck Kwang On 9 August 2013 16:53, Edmund Welter edmund.wel...@desy.de wrote: Dear Teck Kwang Choo, it is the ratio of the number of (in your case) iron atoms. This ratio has no unit. You will therefore get the same number if you calculate molar % ratio or weight % (Except you consider the weight of the missing electron in Fe3+... :-). Now, if you weigh your standards and want to calculate the number of Fe atoms you have to consider the weight of the oxygen. That means, the ratio you get from LCF fitting of your XAS spectra is NOT the ratio between mol of FeO and Fe2O3, but mol FeII+ to mol FeIII+! However, if necessary or usefull you can always calculate the latter from the FeII/FeIII ratio using the molar weights. So, as a chemist I would say, stay consequently with the molar ratio and you are on the safe side. You can always multiply the number of mol with the molar weight, but you would only make things more complicated and end up with the same ratio or, after multiplying with 100, percentage. Concerning the deviation between your result and your expectation: I would be more nervous about the choice of reference substances. If you only use FeO and Fe2O3 your result is only correct if your sample contains no other Fe component than these two. If it contains significant amounts of any other Fe component (even other oxides) you would better not draw any important conclusions from the result of your analysis. Best regards Edmund Welter On 09.08.2013 05:37, Teck Kwang Choo wrote: Hello, I have been using ATHENA to perform Linear Combination Fitting (LCF) on my XANES spectrum to quantify the amounts of Fe (II) and Fe (III) in my samples using only FeO and Fe2O3 as standards. The results showed a majority of Fe (II), which is contrary to what was expected. This made me wonder if the LCF results from XANES is a molar percentage (mol %) or weight percentage (wt%). Could anyone enlighten me on this matter? Thanks! -- Teck Kwang Choo PhD Student Department of Chemical Engineering Room 225, Building 36 Monash University Mobile No.: 04-11489904 ___ Ifeffit mailing listifef...@millenia.cars.aps.anl.govhttp://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 -- 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] Linear Combination Fitting using ATHENA
Hello, I have been using ATHENA to perform Linear Combination Fitting (LCF) on my XANES spectrum to quantify the amounts of Fe (II) and Fe (III) in my samples using only FeO and Fe2O3 as standards. The results showed a majority of Fe (II), which is contrary to what was expected. This made me wonder if the LCF results from XANES is a molar percentage (mol %) or weight percentage (wt%). Could anyone enlighten me on this matter? Thanks! -- 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
