Dear Colleagues, I need to perform XAFS measurements microemulsions (liquid). As I do not have a liquid cell for the in situ XAFS measurements, I would like to know more about liquid cells. Could anyone shoot its cell and send me the photo? I am designing a cell where you optimize the edge jump by modifying the optical path. Thank you very much for your kind attention Renato Canha Ambrosio ---------- Original Message ----------- From: ifeffit-request@millenia.cars.aps.anl.gov To: ifeffit@millenia.cars.aps.anl.gov Sent: Thu, 22 Mar 2007 17:45:00 -0500 Subject: Ifeffit Digest, Vol 49, Issue 14

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Today's Topics:

1. Re: EXAFS reference materials (Frenkel, Anatoly) 2. Re: EXAFS reference materials (Scott Calvin) 3. Re: EXAFS reference materials (Frenkel, Anatoly) 4. Some more questions (Shantanu Behera) 5. Re: Some more questions (Bruce Ravel)

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Message: 1 Date: Thu, 22 Mar 2007 15:28:55 -0400 From: "Frenkel, Anatoly" Subject: Re: [Ifeffit] EXAFS reference materials To: Cc: Ifeffit@millenia.cars.aps.anl.gov Message-ID: <0D9ED6BC247DA847A3855B6726D6E34421854C@exchangemb1.bnl.gov> Content-Type: text/plain; charset="iso-8859-1"

Hi Ruoshuang,

I am cc'ing this email to IFEFFIT mailing list. There are several reasons (I am listing just a few) you should measure a reference sample simultaneously with unknown materials.

1) to align the unknown sample scans prior to merging. If those data are noisy, reference sample can be used for the alignment. In addition, if you want to compare samples before and after some changes that may affect their energy positions (e.g., oxidation, reduction, doping, metal-insulator transition, etc.) you want to align all of their references to reliably analyze these changes.

For this purpose, it does not matter whether you use a metal or a metal oxide or any other standard with the same resonant element.

2) to find S02 value. It is usually the same in most samples which have the same resonant element.

For this purpose, what matters the most is whether you can reliably find S02 from your standard (and then impose it on your unknown sample). Thus, some exotic reference which may still be good for 1) may not be as good for 2) since it may be difficult to refine its structure and get precise value for S02. The metals would be the best, but if you have other materials with "open lattices", e.g., fcc, rock salt, etc., with well defined first shell that you can fit with the miniumum parameters, they will all work fine.

3) to use as a model for your analysis.

If you analyze an alloy, as in your case, you want to compare EXAFS results in your alloys against those in relevant pure compounds. For binary alloys, the best reference will be a pure metal, for ternary - an intermetallic compound, etc. An oxide would not be so useful for modeling. For that reason, people often measure more than one reference, as per 1),2) and 3).

Hope it helps,

Anatoly

________________________________

From: rh2rr@virginia.edu [mailto:rh2rr@virginia.edu] Sent: Thu 3/22/2007 2:54 PM To: Frenkel, Anatoly Subject: EXAFS reference materials

Dear Dr. Frenkel,

I'll do EXAFS on metallic glass but I am not sure about the reference materials. [...] We are trying to study structural relaxation of metallic glass by EXAFS. My samples are Al-TM-RE (TM=Fe,Co,Ni, RE=Gd,Ce,Y). Because Ce and Y are easily oxidized in air, some people suggest use cerium oxide and yttrium oxide as reference materials. My question is: when I do EXAFS measurement and data analysis, is METAL necessary for reference materials, or METAL OXIDE is fine as reference?

Your kind help would be greatly appreciated.

Ruoshuang Huang

------------------- Ruoshuang Huang Research Associate Materials Science and Engineering University of Virginia Phone: 434-982-0238 Fax: 434-982-5799

------------------------------

Message: 2 Date: Thu, 22 Mar 2007 15:48:31 -0400 From: Scott Calvin Subject: Re: [Ifeffit] EXAFS reference materials To: XAFS Analysis using Ifeffit Message-ID: <0JFB006RXLO7QHX0@mta3.srv.hcvlny.cv.net> Content-Type: text/plain; charset=us-ascii; format=flowed

Hi Ruoshuang,

Following up on Anatoly's excellent post, I would say that I personally distinguish between a "reference" and a "standard."

When I talk about a reference, I usually mean something I'm measuring simultaneously with the sample. The primary purpose is energy alignment, although it also gives a check on beam quality issues (e.g. harmonics). For this purpose, I generally use whatever is convenient and well known, such as a metal foil. Sometimes I'll measure the reference by itself, particularly if it's a beamline or edge that is new to me.

On the other hand, I think of a standard as a known compound that is similar to my sample. I often work with nanoparticles, so my standard might be the corresponding bulk material. Or if I'm working with a doped compound, the standard might be the undoped version. The standard is measured under the same conditions as the sample...in fact, that means that I measure the standard with a reference in place, if that makes sense. :)

So I use a reference for Anatoly's purpose (1) and a standard for Anatoly's purposes (2) and (3).

I hope that's helpful.

--Scott Calvin Sarah Lawrence College

At 03:28 PM 3/22/2007, you wrote:

...

Hi Ruoshuang,

I am cc'ing this email to IFEFFIT mailing list. There are several reasons (I am listing just a few) you should measure a reference sample simultaneously with unknown materials.

1) to align the unknown sample scans prior to merging. If those data are noisy, reference sample can be used for the alignment. In addition, if you want to compare samples before and after some changes that may affect their energy positions (e.g., oxidation, reduction, doping, metal-insulator transition, etc.) you want to align all of their references to reliably analyze these changes.

For this purpose, it does not matter whether you use a metal or a metal oxide or any other standard with the same resonant element.

2) to find S02 value. It is usually the same in most samples which have the same resonant element.

For this purpose, what matters the most is whether you can reliably find S02 from your standard (and then impose it on your unknown sample). Thus, some exotic reference which may still be good for 1) may not be as good for 2) since it may be difficult to refine its structure and get precise value for S02. The metals would be the best, but if you have other materials with "open lattices", e.g., fcc, rock salt, etc., with well defined first shell that you can fit with the miniumum parameters, they will all work fine.

3) to use as a model for your analysis.

If you analyze an alloy, as in your case, you want to compare EXAFS results in your alloys against those in relevant pure compounds. For binary alloys, the best reference will be a pure metal, for ternary - an intermetallic compound, etc. An oxide would not be so useful for modeling. For that reason, people often measure more than one reference, as per 1),2) and 3).

------------------------------

Message: 3 Date: Thu, 22 Mar 2007 16:03:34 -0400 From: "Frenkel, Anatoly" Subject: Re: [Ifeffit] EXAFS reference materials To: "XAFS Analysis using Ifeffit" Message-ID: <0D9ED6BC247DA847A3855B6726D6E34421854F@exchangemb1.bnl.gov> Content-Type: text/plain; charset="iso-8859-1"

Thanks, Scott! - Good point. A.

________________________________

From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of Scott Calvin Sent: Thu 3/22/2007 3:48 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] EXAFS reference materials

Hi Ruoshuang,

Following up on Anatoly's excellent post, I would say that I personally distinguish between a "reference" and a "standard."

When I talk about a reference, I usually mean something I'm measuring simultaneously with the sample. The primary purpose is energy alignment, although it also gives a check on beam quality issues (e.g. harmonics). For this purpose, I generally use whatever is convenient and well known, such as a metal foil. Sometimes I'll measure the reference by itself, particularly if it's a beamline or edge that is new to me.

On the other hand, I think of a standard as a known compound that is similar to my sample. I often work with nanoparticles, so my standard might be the corresponding bulk material. Or if I'm working with a doped compound, the standard might be the undoped version. The standard is measured under the same conditions as the sample...in fact, that means that I measure the standard with a reference in place, if that makes sense. :)

So I use a reference for Anatoly's purpose (1) and a standard for Anatoly's purposes (2) and (3).

I hope that's helpful.

--Scott Calvin Sarah Lawrence College

At 03:28 PM 3/22/2007, you wrote:

...

Hi Ruoshuang,

I am cc'ing this email to IFEFFIT mailing list. There are several reasons (I am listing just a few) you should measure a reference sample simultaneously with unknown materials.

1) to align the unknown sample scans prior to merging. If those data are noisy, reference sample can be used for the alignment. In addition, if you want to compare samples before and after some changes that may affect their energy positions (e.g., oxidation, reduction, doping, metal-insulator transition, etc.) you want to align all of their references to reliably analyze these changes.

For this purpose, it does not matter whether you use a metal or a metal oxide or any other standard with the same resonant element.

2) to find S02 value. It is usually the same in most samples which have the same resonant element.

For this purpose, what matters the most is whether you can reliably find S02 from your standard (and then impose it on your unknown sample). Thus, some exotic reference which may still be good for 1) may not be as good for 2) since it may be difficult to refine its structure and get precise value for S02. The metals would be the best, but if you have other materials with "open lattices", e.g., fcc, rock salt, etc., with well defined first shell that you can fit with the miniumum parameters, they will all work fine.

3) to use as a model for your analysis.

If you analyze an alloy, as in your case, you want to compare EXAFS results in your alloys against those in relevant pure compounds. For binary alloys, the best reference will be a pure metal, for ternary - an intermetallic compound, etc. An oxide would not be so useful for modeling. For that reason, people often measure more than one reference, as per 1),2) and 3).

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