Re: [Ifeffit] Ifeffit Digest, Vol 137, Issue 4

Hi Teck Kwang Choo, For PCA analysis you can use SixPack data analysis package by Dr. Sam Webb available at https://home.comcast.net/~sam_webb/sixpack.html. Also you can use Dmeter by Dr Bruce Ravel available at http://bruceravel.github.io/demeter/. With best wishes Dr Abhijeet Gaur On Wed, Jul 2, 2014 at 12:52 PM, wrote:

Send Ifeffit mailing list submissions to ifeffit@millenia.cars.aps.anl.gov

To subscribe or unsubscribe via the World Wide Web, visit http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit or, via email, send a message with subject or body 'help' to ifeffit-request@millenia.cars.aps.anl.gov

You can reach the person managing the list at ifeffit-owner@millenia.cars.aps.anl.gov

When replying, please edit your Subject line so it is more specific than "Re: Contents of Ifeffit digest..."

Today's Topics:

1. spam on our mailing list (Bruce Ravel) 2. Re: to use scattering path in different model or to construct a new model which is the combination of different simple compound (Bruce Ravel) 3. Principal Component Analysis (PCA) for XANES (Teck Kwang Choo) 4. Re: Principal Component Analysis (PCA) for XANES (Amayri, Dr. Samer)

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

Message: 1 Date: Tue, 01 Jul 2014 13:31:59 -0400 From: Bruce Ravel To: XAFS Analysis using Ifeffit Subject: [Ifeffit] spam on our mailing list Message-ID: <53B2F08F.7000401@bnl.gov> Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hi all,

Over the years we've done a pretty good job of keeping spam off this mailing list. As you saw, one slipped through this afternoon. Hopefully it was a one-time event and it will not be necessary to change the friendly nature of security on the list.

B

-- Bruce Ravel ------------------------------------ bravel@bnl.gov

National Institute of Standards and Technology Synchrotron Science Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973

Homepage: http://xafs.org/BruceRavel Software: https://github.com/bruceravel

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

Message: 2 Date: Tue, 01 Jul 2014 15:16:20 -0400 From: Bruce Ravel To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] to use scattering path in different model or to construct a new model which is the combination of different simple compound Message-ID: <53B30904.5030207@bnl.gov> Content-Type: text/plain; charset=ISO-8859-1; format=flowed

On 07/01/2014 10:43 AM, ZHAN Fei wrote:

...

1 In the example,multiplet scattering path comes from two model respectively,if use path from different model in different shell's fit,there is risk of ignore important multiple path across models.Should construct a cluster ,run feff to ensure?

I don't completely understand the question, but I'll give it a try.

In the example of Shelly's paper, she had a situation where she *couldn't* write a single feff.inp file. Her local environment was the average of all possible ways that the uranyl ion could bond to biomass. The uranyl binding disproportionated into a pH-dependent mixture of carboxyl, phosphoryl, and hydroxyl sites. There was simply no way to write a feff.inp file for that. So her solution was to run Feff more than once, picking and choosing paths that represented her best guess for modeling the average bonding environment.

I think what you are really getting at, though, is whether it was right for Shelly to use parts of Feff calculations on a crystals to model something else. If you were to read up on the theory used in Feff, you would find that the important thing is that the muffin tin radii of the scatterers get calculated reasonably. Unless Shelly had a reason to think that the interatomic distances in her biomass sample were VERY different than in the crystals she used to run Feff, then the scattering amplitudes and phase shifts were almost certainly computed quite well enough.

...

2 I have confusion of the relationship pf N between single path and multiple path,for example I think U-Oe-C U-Oe-Pshould be 1 2 respectively,instead 2 4 in paper.

I think Scott's explanation is correct. In real-space, multiple-scattering theory, both ways around a three-legged path have to be counted.

B

-- Bruce Ravel ------------------------------------ bravel@bnl.gov

National Institute of Standards and Technology Synchrotron Science Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973

Homepage: http://xafs.org/BruceRavel Software: https://github.com/bruceravel

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

Message: 3 Date: Wed, 2 Jul 2014 15:59:25 +1000 From: Teck Kwang Choo To: XAFS Analysis using Ifeffit Subject: [Ifeffit] Principal Component Analysis (PCA) for XANES Message-ID: < CAHXRQWDT2LvAsBVBuu7HmAg0oWCC9u8fKBChzDamyw14-uyJ_Q@mail.gmail.com> Content-Type: text/plain; charset="utf-8"

Hi Everyone,

Does anyone know what software I should use to perform a Principal Component Analysis (PCA) on my K-edge XANES spectra (for sulfur)? The reason I need to use this technique is because I have a couple of reference compound spectra but am not sure which of those I should use to fit my unknown sample spectrum.

Any help is appreciated.

Thanks and kind regards.

Teck Kwang Choo PhD Candidate Department of Chemical Engineering Room 225, Building 36 Monash University Mobile No.: 04-11489904