[Ifeffit] Vanadium-Chromium Prussian Blue Analog XANES fitting

[Adora Graham]

Chris,

It looks like your other vanadium papers all seem to involve vanadium
oxides in different oxidation states. While I think this method works very
well for metal oxides, in my case there should only be isocyanides bound,
from the vanadium perspective (not counting defect sites), so I'm not fully
convinced whether or not this method is applicable here. What are your
thoughts?

Thanks,
Adora

On Fri, Jul 31, 2015 at 4:36 AM, Chris Patridge <patridge at buffalo.edu>
wrote:

> If you have Dr. Whittaker-Brooks data then you have the work we did on
> vanadium oxides. You can look at some of the other vanadium papers we did.
>
> Chris
>
> Sent from my iPhone
>
> On Jul 30, 2015, at 11:49 PM, Adora Graham <abaldwin2242 at gmail.com> wrote:
>
> Chris,
>
> I have attached a copy of the correlation plot that I am using. I could
> also send more information as to how I am picking the peaks (which might
> also be the problem here), but that would take significantly more time to
> generate at this point.
>
> I was using the main edge values reported in Wong's paper (in red), since
> one of my standards (VSO4) does not have a pre-edge peak, so it wouldn't be
> comparable. The main edge value I get for VOSO4 differs by ~0.6eV compared
> to Wong's reported value, so I think I'm adjusting things correctly. I
> actually have access to the raw data from J. Mater. Chem., 2011, 21,
> 5580  (with permission from Dr. Whittaker-Brooks), which I am using as
> several of my standards (in black).
>
> I have a feeling that my main issue is the difference in attached atoms
> (CN vs. O) of my compound compared to the standards. What do you think?
>
> Regards,
> Adora
>
> On Thu, Jul 30, 2015 at 6:12 PM, Chris Patridge <patridge at buffalo.edu>
> wrote:
>
>> The standard curve using V standard, how are you making the curve?  You
>> probably know from the Wong paper that there are pre edge features for the
>> vanadium oxide species. We used a very similar method to assign oxidation
>> states to doped vanadium oxide compounds between 3-5. The method gave us
>> results that were consistent with other evidence.
>>
>> Chris
>>
>> Sent from my iPhone
>>
>> On Jul 30, 2015, at 7:38 PM, Adora Graham <abaldwin2242 at gmail.com> wrote:
>>
>> Hello,
>>
>> First of all, I am still very new to XAS analysis, so please excuse any
>> misunderstandings I may have.
>>
>> I have a series of compounds nominally consisting of KxVx[Cr(CN)6]
>> Prussian blue analogs (where x is ~1) with Cr(III) and presumably V(II)
>> present in the system. From other evidence, the V(II) may be oxidizing to
>> V(III). I have XAS data collected at the V and Cr K-edges from APS and have
>> been struggling through trying to analyze my data using Athena.
>>
>> I am trying to get two things out of this data:
>>
>> First, I would like to get the oxidation state of the Vanadium sites. If
>> they are not V(II), to get the ratio of V(II) to V(III) present, if
>> possible. I have been trying to follow a similar analysis to Wong (Phys.
>> Rev. B, 1984, 30, 10, 5596-5610). However, I seem to be running into the
>> issue of finding standards with a similar ligand set to my sample. I have
>> XAS data for the following standards: VO, V2O3, V2O4, V2O5, V(acac)3,
>> VO(acac), VOSO4, and VSO4. I start with VSO4 as my initial vanadium source,
>> so that could be useful for a comparison. Our initial idea was to use the
>> vanadium oxides to give a standard curve to then extrapolate the oxidation
>> state of my compound, but using this gives me an oxidation state of ~4.2
>> which seems unreasonable for my system. I am kind of lost otherwise as to
>> what else I could do with this.
>>
>> Second, I would like to get the ratio of V to Cr. I was told I could
>> compare the un-normalized K-edge heights of the vanadium to that of the
>> chromium to get this ratio. This doesn't seem right, as I would think that
>> there should be some relative intensity factor involved. Also, this gives
>> me a fairly unreasonable value of 4:1, since XPS measurements give me
>> values of around 1:1.
>>
>> Can you point me in the right direction for these issues?
>>
>> I've also attached the project files for one of my samples.
>>
>> Thanks,
>> Adora
>>
>> <AGB02-083-Cr merged.prj>
>>
>> <AGB02-083-V merged.prj>
>>
>> _______________________________________________
>> Ifeffit mailing list
>> Ifeffit at millenia.cars.aps.anl.gov
>> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>>
>>
>> _______________________________________________
>> Ifeffit mailing list
>> Ifeffit at millenia.cars.aps.anl.gov
>> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>>
>>
> <XAS main edge correlations.pdf>
>
> _______________________________________________
> Ifeffit mailing list
> Ifeffit at millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>
>
> _______________________________________________
> Ifeffit mailing list
> Ifeffit at millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20150731/9835200c/attachment.html>