Hi Chris,
The term N*S02 is fitted for each path of the FEFF calculation. So my question is, even if we know N with a great certainty for some path, how can we vary both N and S02 for other paths ? or Did I understand it wrong ?
Best regards,
Jatin
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1. Re: Breaking down correlationships between parameters
(Rana, Jatinkumar Kantilal)
2. Re: Breaking down correlationships between parameters
(Chris Patridge)
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Date: Mon, 23 Mar 2015 11:00:19 +0000
From: "Rana, Jatinkumar Kantilal"
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Subject: Re: [Ifeffit] Breaking down correlationships between
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Hi Scott,
Thank you for your comments. Can you please elaborate a little bit more on this "In cases like that, both N for all paths but one and S02 can be fit without 100% correlation."
Best regards,
Jatin
-----Original Message-----
From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of ifeffit-request@millenia.cars.aps.anl.gov
Sent: 23 March, 2015 10:16
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Subject: Ifeffit Digest, Vol 145, Issue 41
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Today's Topics:
1. Re: Breaking down correlationships between parameters
(Scott Calvin)
2. Re: Breaking down correlationships between parameters
(Matt Newville)
3. Re: Breaking down correlationships between parameters
(Rana, Jatinkumar Kantilal)
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Message: 1
Date: Sun, 22 Mar 2015 13:44:28 -0400
From: Scott Calvin
To: XAFS Analysis using Ifeffit
Subject: Re: [Ifeffit] Breaking down correlationships between
parameters
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One side-comment from me:
On Mar 22, 2015, at 12:52 PM, Matt Newville mailto:newville@cars.uchicago.edu> wrote:
N and S02 are always 100% correlated (mathematically, not merely by the finite k range).
Matt is saying that N and S02 are always 100% correlated for a single path. But in some situations you might know N for one path but not others. For example, you might know that the absorbing atom is octahedrally coordinated to oxygen but not be as certain as to next-nearest neighbors, or that there are copper atoms on the corners of a simple cubic lattice with a mixture of atoms at other positions. In cases like that, both N for all paths but one and S02 can be fit without 100% correlation.
The degeneracy of multiple-scattering paths can often be constrained in terms of the coordination numbers for direct-scattering paths, which can further reduce (not ?break?) the correlation.
In terms of the main question, I agree with Matt: I don?t think there?s much point in using the line-crossing technique nowadays; fitting using multiple k-weights simultaneously accomplishes the same thing but is a bit easier to interpret statistically.
?Scott Calvin
Sarah Lawrence College
