Re: [Ifeffit] XANES temperature estimation (Robert Gordon)
Hi Gordon, I have just one spectrum per sample, all taken at different T (unknown, due to technical problems) and P (known). I'd like to find T and using an EoS is not a viable option. I was thinking that maybe, assuming that the Debye-Waller term is explained only by thermal disorder, the Debye temperature is P independent, and there are no structural or electronic transformations, I could retrieve T by fitting the Debye-Waller term and using the reference spectra. Is this possible? Best regards Gabriele
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Message: 1 Date: Mon, 21 Nov 2022 16:16:50 +0100 From: Gabriele GAROFALO
To: ifeffit@millenia.cars.aps.anl.gov Subject: [Ifeffit] XANES temperature estimation Message-ID: <0ce690cc-ca47-5507-76b3-848bba8d7db8@esrf.fr> Content-Type: text/plain; charset=UTF-8; format=flowed Hi everyone,
I'd like to estimate the temperature of some samples from some XANES spectra, is there a way to do that? I couldn't find an answer in the mailing list archive.
Thanks!
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Message: 2 Date: Mon, 21 Nov 2022 10:23:10 -0500 From: Anatoly Frenkel
To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] XANES temperature estimation Message-ID: Content-Type: text/plain; charset=utf-8 Only evaporation temperature, when XANES spectrum disappears?:)
Anatoly
On Nov 21, 2022, at 10:20 AM, Gabriele GAROFALO
wrote: ?Hi everyone,
I'd like to estimate the temperature of some samples from some XANES spectra, is there a way to do that? I couldn't find an answer in the mailing list archive.
Thanks!
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Message: 3 Date: Mon, 21 Nov 2022 09:13:19 -0800 From: Robert Gordon
To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] XANES temperature estimation Message-ID: Content-Type: text/plain; charset="utf-8" Hi Gabriele,
To qualify Anatoly's cheerful, pre-morning coffee response, if your samples are part of a sequence of measurements of a material whose XANES has been measured at different temperatures, and said XANES does have some changes owing to changes in physical or electronic behavior with temperature (i.e. a phase transition), then you could estimate where your samples fit within that determined behavior.
Are you familiar with how temperature dependence manifests in a typical XAFS measurement? ...through the Debye-Waller term..the effects of which become less pronounced at lower k...
Temperature is more typically a controlled parameter during measurements.
So no, not really...unless there is a known behavior for comparison.
-R.
Hi Gabriele, On Mon, Nov 21, 2022 at 12:59 PM Gabriele Garofalo < gabriele.garofalo@esrf.fr> wrote:
Hi Gordon,
I have just one spectrum per sample, all taken at different T (unknown, due to technical problems) and P (known). I'd like to find T and using an EoS is not a viable option. I was thinking that maybe, assuming that the Debye-Waller term is explained only by thermal disorder, the Debye temperature is P independent, and there are no structural or electronic transformations, I could retrieve T by fitting the Debye-Waller term and using the reference spectra. Is this possible?
It seems unlikely to me. XANES is typically described as probing the electronic states of a sample. There is, of course, a strong connection between atomic/nuclear structure and electronic structure, but the changes in thermal structural disorder with temperature are actually pretty small. Interference-sensitive measurements (EXAFS, XRD) will be sensitive to such changes, but XANES is much less so. When describing an EXAFS Deybe-Waller model, the amplitude decays as exp(-2k^2*sigma^2). When k is very small (ie, XANES), you need to have sigma be very large for that to make much of an impact in the XANES region. Some XANES features (such as pre-edge peak intensities) can have some temperature dependence - these are sensitive to small changes in the overlap of specific electronic levels. But, in general, the XANES features don't have a strong temperature dependence. But, I guess we should ask: do you see a significant variation in your XANES spectra with temperature? --Matt
participants (2)
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Gabriele Garofalo
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Matt Newville