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Today's Topics:
1. Re: Ifeffit Digest, Vol 150, Issue 2 (Abhijeet Gaur)
2. Re: Measuring particle size by coordination number (Maxim Boyanov)
3. Re: Measuring particle size by coordination number
(Anatoly I Frenkel)
----------------------------------------------------------------------
Message: 1
Date: Mon, 3 Aug 2015 13:49:40 +0200
From: Abhijeet Gaur <abhijeetgaur9@gmail.com>
To: ifeffit <ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] Ifeffit Digest, Vol 150, Issue 2
Message-ID:
<CAEq27Q1Fde2qTQyrgaAMaTJ1wUpoXydxOcS0v73MPXdAKJs_zA@mail.gmail.com>
Content-Type: text/plain; charset="utf-8"
Hi Scott,
Thanks for your quick reply. So, I have to add more paths to
the fitting and then try to determine the size of the particle.
Also, I want to add some analysis details to confirm that I am
on the right path.
The value of amp is obtained from fitting of metal foil, i.e.,
0.84 (0.03) and is kept fixed during the fitting of the sample.
S02 is defined by the formula S02 =
amp*(1-(0.75*(Reff/R))+(0.063*(Reff*Reff*Reff/(R*R*R)))).
With thanks
Abhijeet
>
>
> Message: 2
> Date: Mon, 3 Aug 2015 07:11:53 -0400
> From: Scott Calvin <scalvin@sarahlawrence.edu>
> To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov>
> Subject: Re: [Ifeffit] Measuring particle size by coordination number
> Message-ID: <C61F6046-713C-4EC2-8F7A-536ECC43DEA5@slc.edu>
> Content-Type: text/plain; charset="utf-8"
>
> Hi Abhijeet,
>
> The formula looks poorly when it is only applied with one path.
>
> The strength of this approach, and of Anatoly Frenkel?s alternative
> strategy for finding particle sizes, is that it compares coordination
> numbers for different shells, helping to break the correlations between N,
> S02, and sigma2.
>
> Even then, it tends to report sizes that are small compared to those
> provided by other techniques, but compares sizes between different samples
> quite well.
>
> ?Scott Calvin
> Sarah Lawrence College
>
>
>
--
*Dr. Abhijeet Gaur*
*Post doctoral fellow in the Institute for Chemical Technology and Polymer
Chemistry *
*Karlsruher Institut f?r Technologie (KIT), Karlsruhe Germany.*
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Message: 2
Date: Mon, 3 Aug 2015 10:54:05 -0500
From: "Maxim Boyanov" <mboyanov@nd.edu>
To: "'XAFS Analysis using Ifeffit'"
<ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] Measuring particle size by coordination number
Message-ID: <001a01d0ce04$a13d13f0$e3b73bd0$@nd.edu>
Content-Type: text/plain; charset="utf-8"
An additional reason for the discrepancy in particle sizes between EXAFS and TEM may be that TEM detects only particles above a cut-off size, whereas particles of all sizes (including single ion complexes) contribute to the EXAFS signal. Assuming that EXAFS is 100% accurate in determining particle size ;-), this would result in smaller sizes reported by EXAFS and will be noticeable if a significant fraction of the atoms are in particles with sizes below the detection limit of TEM.
-Max
From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Scott Calvin
Sent: Monday, August 3, 2015 6:12 AM
To: XAFS Analysis using Ifeffit
Subject: Re: [Ifeffit] Measuring particle size by coordination number
Hi Abhijeet,
The formula looks poorly when it is only applied with one path.
The strength of this approach, and of Anatoly Frenkel?s alternative strategy for finding particle sizes, is that it compares coordination numbers for different shells, helping to break the correlations between N, S02, and sigma2.
Even then, it tends to report sizes that are small compared to those provided by other techniques, but compares sizes between different samples quite well.
?Scott Calvin
Sarah Lawrence College
On Aug 3, 2015, at 4:41 AM, Abhijeet Gaur <abhijeetgaur9@gmail.com <mailto:abhijeetgaur9@gmail.com> > wrote:
Hi all,
Sorry, I may be asking a question already asked in the mailing list, but I am unable to get it from the earlier discussions.
I am reading one of the research article ?? Determination of crystallite size in a magnetic nanocomposite using extended x-ray absorption fine structure?? .J. Appl. Phys,. vol 94, page 778, 2003
In this paper there is a formula N_nano = [1-3/4(r/R)+1/16(r/R)^3]N_bulk, which you said can be used in the Artemis for extracting the particle size.
I am trying to use this formula for determination of size of Ni particles in an Ni / Al2O3 catalyst. From TEM the size determined is around 4 nm.
So, I am trying to fit the theoretical model of Ni metal to the sample data in the Artemis
I defined a guessed parameter R and then put the whole formula for S02 = amp*(1-(0.75*(Reff/R))+(0.063*(Reff*Reff*Reff/(R*R*R)))).
The value of R I am getting is 0.81 (0.05) which is quite small.
Is there something I am missing in the formula or I have to define the N seprately for sample cooridnation number.
Currently, I am using only the first path in the fitting.
With thanks
Abhijeet Gaur
--
Dr. Abhijeet Gaur
Post doctoral fellow in the Institute for Chemical Technology and Polymer Chemistry
Karlsruher Institut f?r Technologie (KIT), Karlsruhe Germany.
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Message: 3
Date: Mon, 3 Aug 2015 16:02:28 +0000
From: Anatoly I Frenkel <afrenke2@yu.edu>
To: XAFS Analysis using Ifeffit <ifeffit@millenia.cars.aps.anl.gov>
Subject: Re: [Ifeffit] Measuring particle size by coordination number
Message-ID:
<545F89325F51764C902D37B42C9F4D53017CC2BF8E@YUWEXCPM11.yuad.uds.yu.edu>
Content-Type: text/plain; charset="windows-1252"
As an illustration of the very good comment that Max just made, here is a recent paper that explains this discrepancy in detail, and proposes a remedy.
Anatoly
Sent from my mobile phone, please forgive typos
----- Reply message -----
From: "Maxim Boyanov" <mboyanov@nd.edu>
To: "'XAFS Analysis using Ifeffit'" <ifeffit@millenia.cars.aps.anl.gov>
Subject: [Ifeffit] Measuring particle size by coordination number
Date: Mon, Aug 3, 2015 11:59 AM
An additional reason for the discrepancy in particle sizes between EXAFS and TEM may be that TEM detects only particles above a cut-off size, whereas particles of all sizes (including single ion complexes) contribute to the EXAFS signal. Assuming that EXAFS is 100% accurate in determining particle size ;-), this would result in smaller sizes reported by EXAFS and will be noticeable if a significant fraction of the atoms are in particles with sizes below the detection limit of TEM.
-Max
From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Scott Calvin
Sent: Monday, August 3, 2015 6:12 AM
To: XAFS Analysis using Ifeffit
Subject: Re: [Ifeffit] Measuring particle size by coordination number
Hi Abhijeet,
The formula looks poorly when it is only applied with one path.
The strength of this approach, and of Anatoly Frenkel?s alternative strategy for finding particle sizes, is that it compares coordination numbers for different shells, helping to break the correlations between N, S02, and sigma2.
Even then, it tends to report sizes that are small compared to those provided by other techniques, but compares sizes between different samples quite well.
?Scott Calvin
Sarah Lawrence College
On Aug 3, 2015, at 4:41 AM, Abhijeet Gaur <abhijeetgaur9@gmail.com<mailto:abhijeetgaur9@gmail.com>> wrote:
Hi all,
Sorry, I may be asking a question already asked in the mailing list, but I am unable to get it from the earlier discussions.
I am reading one of the research article ?? Determination of crystallite size in a magnetic nanocomposite using extended x-ray absorption fine structure?? .J. Appl. Phys,. vol 94, page 778, 2003
In this paper there is a formula N_nano = [1-3/4(r/R)+1/16(r/R)^3]N_bulk, which you said can be used in the Artemis for extracting the particle size.
I am trying to use this formula for determination of size of Ni particles in an Ni / Al2O3 catalyst. From TEM the size determined is around 4 nm.
So, I am trying to fit the theoretical model of Ni metal to the sample data in the Artemis
I defined a guessed parameter R and then put the whole formula for S02 = amp*(1-(0.75*(Reff/R))+(0.063*(Reff*Reff*Reff/(R*R*R)))).
The value of R I am getting is 0.81 (0.05) which is quite small.
Is there something I am missing in the formula or I have to define the N seprately for sample cooridnation number.
Currently, I am using only the first path in the fitting.
With thanks
Abhijeet Gaur
--
Dr. Abhijeet Gaur
Post doctoral fellow in the Institute for Chemical Technology and Polymer Chemistry
Karlsruher Institut f?r Technologie (KIT), Karlsruhe Germany.
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