Hi,
I am working with a molten salt system with Nickel Chloride as one of the
components. If you have measured XAS data on anhydrous and hydrated Nickel
Chloride at RT and 320C, I would really appreciate if you could share the raw
data with me.
Thanks in advance for your help!
Simer
Simerjeet K Gill,
Materials Scientist,
Nuclear Science and Technology Department,
Brookhaven National Lab,
Upton, NY 11973
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Contents of Ifeffit digest..."
Today's Topics:
1. Re: Standard deviation of R value (Matt Newville)
2. Re: Standard deviation of R value (Anatoly Frenkel)
3. Re: Standard deviation of R value (Erin Finley)
----------------------------------------------------------------------
Message: 1
Date: Fri, 11 Jan 2019 10:04:49 -0600
From: Matt Newville <newvi...@cars.uchicago.edu>
To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] Standard deviation of R value
Message-ID:
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Hi Erin,
On Fri, Jan 11, 2019 at 8:19 AM Erin Finley <efinley9...@gmail.com> wrote:
> Hello, I see in many publications the R value reported with a standard
> deviation. However, when I look at my resulting data from a fit I
> don't see one listed. I am still new to EXAFS research and so I am
> wondering where I can get this information. I am assuming I need to
> calculate it from another parameter I am just not sure which one.
>
>
The uncertainties in R are typically in the fit report. But also, we typically
refine a "delR" parameter that is R - Reff, where Reff is the distance (half
path-lengh) for the scattering path. So, if you don't see an uncertainty
reported for R but do see an uncertainty for delR (or whatever parameter name
you used), use that. The uncertainty in R will
(normally) be the uncertainty in delR.
If I'm misunderstanding the question, pleas give more details about what you
are doing.
--Matt
Thanks for your help!
> Cheers,
>
> --
> Erin Finley
> PhD Candidate
> Brgoch Research Group
> Department of Chemistry
> University of Houston
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> Ifeffit mailing list
> Ifeffit@millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
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--
--Matt Newville <newville at cars.uchicago.edu> 630-252-0431
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Message: 2
Date: Fri, 11 Jan 2019 11:18:03 -0500
From: Anatoly Frenkel <anatoly.fren...@stonybrook.edu>
To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] Standard deviation of R value
Message-ID:
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As an additional comment, it is a murky issue whether the reported thing
together with R is the standard deviation. It is not easy to find it in the
literature but there are some papers dating back to the 1990s that state that
the uncertainties reported in the EXAFS fitting results correspond to the 95%
confidence level which means 2 standard deviations for an approximately normal
data set. I don't think it is correct. Regardless whether the distribution of
some or all fitting variables are treated by the Levenburg-Marquartd method as
normal or not, the reported error is really not a standard deviation but a
square root of the element in a covariance matrix. What is the relationship of
that and the standard deviation of the fitting variable is one of the few
remaining unsolved mysteries in EXAFS analysis.
Anatoly
On Fri, Jan 11, 2019 at 11:05 AM Matt Newville <newvi...@cars.uchicago.edu>
wrote:
> Hi Erin,
>
> On Fri, Jan 11, 2019 at 8:19 AM Erin Finley <efinley9...@gmail.com> wrote:
>
>> Hello, I see in many publications the R value reported with a
>> standard deviation. However, when I look at my resulting data from a
>> fit I don't see one listed. I am still new to EXAFS research and so I
>> am wondering where I can get this information. I am assuming I need
>> to calculate it from another parameter I am just not sure which one.
>>
>>
> The uncertainties in R are typically in the fit report. But also, we
> typically refine a "delR" parameter that is R - Reff, where Reff is
> the distance (half path-lengh) for the scattering path. So, if you
> don't see an uncertainty reported for R but do see an uncertainty for
> delR (or whatever parameter name you used), use that. The uncertainty
> in R will
> (normally) be the uncertainty in delR.
>
> If I'm misunderstanding the question, pleas give more details about
> what you are doing.
>
> --Matt
>
>
>
>
>
>
> Thanks for your help!
>> Cheers,
>>
>> --
>> Erin Finley
>> PhD Candidate
>> Brgoch Research Group
>> Department of Chemistry
>> University of Houston
>> _______________________________________________
>> Ifeffit mailing list
>> Ifeffit@millenia.cars.aps.anl.gov
>> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>> Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit
>>
>
>
> --
> --Matt Newville <newville at cars.uchicago.edu> 630-252-0431
> _______________________________________________
> Ifeffit mailing list
> Ifeffit@millenia.cars.aps.anl.gov
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Message: 3
Date: Fri, 11 Jan 2019 10:22:41 -0600
From: Erin Finley <efinley9...@icloud.com>
To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] Standard deviation of R value
Message-ID: <14556591-aa95-4ebb-b264-fc6bf1386...@icloud.com>
Content-Type: text/plain; charset="us-ascii"
Thanks Matt! That makes perfect sense and what I had thought may be the case.
Erin
> On Jan 11, 2019, at 10:04 AM, Matt Newville <newvi...@cars.uchicago.edu>
> wrote:
>
> Hi Erin,
>
>> On Fri, Jan 11, 2019 at 8:19 AM Erin Finley <efinley9...@gmail.com> wrote:
>> Hello, I see in many publications the R value reported with a standard
>> deviation. However, when I look at my resulting data from a fit I don't see
>> one listed. I am still new to EXAFS research and so I am wondering where I
>> can get this information. I am assuming I need to calculate it from another
>> parameter I am just not sure which one.
>>
>
> The uncertainties in R are typically in the fit report. But also, we
> typically refine a "delR" parameter that is R - Reff, where Reff is the
> distance (half path-lengh) for the scattering path. So, if you don't see an
> uncertainty reported for R but do see an uncertainty for delR (or whatever
> parameter name you used), use that. The uncertainty in R will (normally) be
> the uncertainty in delR.
>
> If I'm misunderstanding the question, pleas give more details about what you
> are doing.
>
> --Matt
>
>
>
>
>
>
>> Thanks for your help!
>> Cheers,
>>
>> --
>> Erin Finley
>> PhD Candidate
>> Brgoch Research Group
>> Department of Chemistry
>> University of Houston
>> _______________________________________________
>> Ifeffit mailing list
>> Ifeffit@millenia.cars.aps.anl.gov
>> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>> Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit
>
>
> --
> --Matt Newville <newville at cars.uchicago.edu> 630-252-0431
> _______________________________________________
> Ifeffit mailing list
> Ifeffit@millenia.cars.aps.anl.gov
> http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
> Unsubscribe: http://millenia.cars.aps.anl.gov/mailman/options/ifeffit
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