Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Teck Kwang Choo]

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  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 
> *To:* XAFS Analysis using Ifeffit 
> *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  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 
>> *To:* XAFS Analysis using Ifeffit 
>>  *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 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  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 repre

Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Matthew Marcus]

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 
  To: XAFS Analysis using Ifeffit 
  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  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 
  To: XAFS Analysis using Ifeffit 
  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  
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  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 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. 





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Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Teck Kwang Choo]

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  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 
> *To:* XAFS Analysis using Ifeffit 
> *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 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  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>> 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

Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Matthew Marcus]

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 
  To: XAFS Analysis using Ifeffit 
  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  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  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 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.





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--
Teck Kwang Choo
PhD Student
Department of Chemical Engineering
Room 225, Building 36
Monash University
Mobile No.: 04-11489904



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Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Matthew Marcus]

One spectrum was taken in fluorescence mode (maghemite), the other in 
electron-yield
mode.  Yes, it's OK to do that on pre-edge subtracted, normalized spectra, 
which is what I sent.
mam
  - Original Message - 
  From: Teck Kwang Choo 
  To: XAFS Analysis using Ifeffit 
  Sent: Tuesday, August 13, 2013 5:07 PM
  Subject: Re: [Ifeffit] Linear Combination Fitting using ATHENA


  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  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 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.





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  --
  Teck Kwang Choo
  PhD Student
  Department of Chemical Engineering
  Room 225, Building 36
  Monash University
  Mobile No.: 04-11489904



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  -- 
  Teck Kwang Choo
  PhD Student
  Department of Chemical Engineering
  Room 225, Building 36
  Monash University
  Mobile No.: 04-11489904



--


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Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Teck Kwang Choo]

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  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  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>> 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 >> TMAG.2009.2018880  <
>>> http://dx.doi.org/10.1109/**TMAG.2009.2018880
>>> >>
>>>
>>> Alexandre.
>>>
>>>
>>>
>>>
>>>
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>>> >
>>>
>>>
>>>
>>>
>>>
>>> --
>>> Teck Kwang Choo
>>> PhD Student
>>> Department of Chemical Engineering
>>> Room 225, Building 36
>>> Monash University
>>> Mobile No.: 04-11489904
>>>
>>>
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>>>
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>>
>>
>
>
> --
> Teck Kwang Choo
> PhD Student
> Department of Chemical Engineering
> Room 225, Building 36
> Monash University
> M

Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Teck Kwang Choo]

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  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>> 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 > TMAG.2009.2018880  <
>> http://dx.doi.org/10.1109/**TMAG.2009.2018880
>> >>
>>
>> Alexandre.
>>
>>
>>
>>
>>
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>> http://millenia.cars.aps.anl.**gov/mailman/listinfo/ifeffit
>> >
>>
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>> 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
>>
>>
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>


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Monash University
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Re: [Ifeffit] Linear Combination Fitting using ATHENA

[María Elena Montero Cabrera]

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" 
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  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 
>>> 
>>> >
>>>
>>> Alexandre.
>>>
>>>
>>>
>>>
>>> __**_
>>> Ifeffit mailing list
>>> ifef...@millenia.cars.aps.anl.**gov 
>>> http://millenia.cars.aps.anl.**gov/mailman/listinfo/ifeffit
>>>
>>>  __**_
>> Ifeffit mailing list
>> ifef...@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
>
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Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Matthew Marcus]

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 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 >

Alexandre.




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PhD Student
Department of Chemical Engineering
Room 225, Building 36
Monash University
Mobile No.: 04-11489904


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#%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)
#%Time&date: 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
7.1

Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Teck Kwang Choo]

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  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 
>> 
>> >
>>
>> Alexandre.
>>
>>
>>
>>
>> __**_
>> Ifeffit mailing list
>> ifef...@millenia.cars.aps.anl.**gov 
>> http://millenia.cars.aps.anl.**gov/mailman/listinfo/ifeffit
>>
>>  __**_
> Ifeffit mailing list
> ifef...@millenia.cars.aps.anl.**gov 
> http://millenia.cars.aps.anl.**gov/mailman/listinfo/ifeffit
>



-- 
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PhD Student
Department of Chemical Engineering
Room 225, Building 36
Monash University
Mobile No.: 04-11489904
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Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Latta, Drew E.]

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.gov<mailto: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.2009.2018880<http://dx.doi.org/10.1109/TMAG.2009.2018880>

Alexandre.

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Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Alexandre dos Santos Anastacio]

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 

Alexandre.
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Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Teck Kwang Choo]

That's magnetite unfortunately!


On 12 August 2013 14:02, Scott Calvin  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  > 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.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
>
>
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>
>
>
> --
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> PhD Student
> Department of Chemical Engineering
> Room 225, Building 36
> Monash University
> Mobile No.: 04-11489904
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Department of Chemical Engineering
Room 225, Building 36
Monash University
Mobile No.: 04-11489904
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Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Teck Kwang Choo]

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  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 
>> http://millenia.cars.aps.anl.**gov/mailman/listinfo/ifeffit
>>
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>



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Department of Chemical Engineering
Room 225, Building 36
Monash University
Mobile No.: 04-11489904
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Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Teck Kwang Choo]

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  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
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Re: [Ifeffit] Linear Combination Fitting using ATHENA

[Edmund Welter]

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

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[Ifeffit] Linear Combination Fitting using ATHENA

[Teck Kwang Choo]

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
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