- Ifeffit - millenia.cars.aps.anl.gov

Re: [Ifeffit] SIXPACK
by Matt Newville 13 Feb '09

13 Feb '09

Hi Bounif, I'm actually not responsible for the PCA analysis part of SixPACK, Sam Webb (the author of SixPACK!) is. And I have to admit I don't know all the details beyond what is documented at: http://www-ssrl.slac.stanford.edu/~swebb/spdocs/sixpack_documentation.htm#P… I'll try to answer your questions, and hopefully Sam or someone on this list will correct me: > My question is the following one: > When I calculate the principals components from the data matrix ( sampls ) > I must make a target transformation to obtain the réels compoents which > constitutes mixtures. > 1-a reels components are obtained by the transformationof the principals > components or de target components? I believe it uses the components found from PCA as the pieces with which to build a spectra that matches the target. > 2-How to calculate the concentration of the reels constituents ? I am not sure how to get those numbers directly. If the target transformation works to reproduce your spectra, you could always then try linear combinations to get the sample constituents. I'm not sure that this is guaranteed to work or give a unique answer (say, if all of your samples were truly mixtures of multiple components themselves), but I think that it does normally work in practice with a small number of components and some of them "nearly" endmembers. Cheers, --Matt Newville <newville at cars.uchicago.edu> 2009/2/11 bounif <bounif(a)univ-paris12.fr>: > Dear Newville, > With big enjoyment which I writes you,I am a student in paris 12 > université,I work on the decomposition of the spectre EXAFS of mixtures at > several pure constituents,I test various methods, Among these methods the > principals components analisis(PCA).For this, I use the SIXPACK software > which you are the author. > My question is the following one: > When I calculate the principals components from the data matrix ( sampls ) > I must make a target transformation to obtain the réels compoents which > constitutes mixtures. > 1-a reels components are obtained by the transformationof the principals > components or de target components? > 2-How to calculate the concentration of the reels constituents ? > Very cordially > > > cher Newville, > avec grande joie que je vous écrit,je suis un doctorant à luniversité de > paris 12,je travail sur la décomposition des spectre EXAFS des mélanges en > plusieurs composantes pures,je test différentes méthodes,parmi ces > méthodes l'analyse en composantes principale.pour cela j'utilise le logiciel > SIXPACK dont vous êtes l'auteur. > Ma question est la suivante:quand je calcule les composantes principales > (components) à partir de la matrice des donnés (sampls) je dois effectuer un > transformation pour obtenir les composés réels qui constitue les mélanges. > 1-les composés réel sont obtenus par la transformation des composantes > principales où les composantes cible (target ) ? > 2-comment calculer la concentration des composantes réel? > bien cordialement > > > > > > Bounif Mohamed > > Institut de Chimie et des Matériaux Paris Est (ICMPE) > UMR CNRS-Université Paris 12 n° 7182 > Equipe SAX > 2 à 8 Rue Henri Dunant, 94320 THIAIS France > Tel : +33.1.49.78.13.38 > Fax : +33.1.49.78.12.03 > > > > >

3 2

Re: [Ifeffit] Mo EXAFS
by Matt Newville 13 Feb '09

13 Feb '09

Dear Mehdi, Sorry for taking so long to respond, and hope you'll again forgive me for forwarding this message to the Ifeffit mailing list. I actually have taken very little data on Mo compounds. I don't know what is in the Lytel database for the compounds you list, either. But I'll bet that someone on this list can help you out.... --Matt Mehdi Monir <MXM785(a)bham.ac.uk> wrote: > Dear Matthew > > I am a PhD research student in metallurgy and materials dept. at University of Birmingham . I am working under supervision of Dr. Alison J. Davenport (University of Birmingham) and Prof. Trevor Rayment(Diamond light source). > We are working on a project which is part of an EPSRC -funded program to characterize the chemistry and structure of salt films on Fe, Ni and stainless steel in chloride base solutions with and without other anions, and to explore the use of X-Ray absorption spectroscopy for characterizing chemistry of pits in these materials. > We have done XAS experiments on Mo edge this september at Diamond light source(Synchrotron Facility, Oxfordshire, UK).I am looking for Mo standard spectra like Mo foil, MoAcetate, MoCl3, MoO2, MoCl5 and Na2MoO4 in HCl solutions but unfortunately couldn't find too many ref spectra. > It would be really great help if give me any idea or introduce any resources to find these information. > > Many Thanks > > Mehdi > >

2 1

Co doped znO
by Guvenc Akgul (gakgul) 12 Feb '09

12 Feb '09

dear all I want to figure out and plot theorical Co doped ZnO using FEFF8. how can I do it? thanks guven

2 1

Artemis fitting problem
by abhijeet gaur 07 Feb '09

07 Feb '09

Hi Scott, I know that alpha is not a temperature expansion coefficient .I guess it is a volume expansion coefficient( tell me if I am right). Actually I want to know that is it necessary to fit Ei, 3rd, 4th, cumulant in the fitting procedure .If yes then please tell me how to get them involve in the fit .when I give parameter like guess 3rd, guess 4th . Artemis dont take them . And about Ei I am completely blank.I dont know how to use it and from where i will get it. One more thing is that I am fitting Cu foil, CuO and Cu2O , so how many number of paths should I take . And Thanks a lot for your suggestions With regards Abhijeet

1 0

Lost second shell
by Eugenio Otal 06 Feb '09

06 Feb '09

Hi Carlo, thanks for for help, really interesting your paper about ZnMnO. Cheers, euG

1 0

Co2MnO4 atoms.inp files
by JeongEunSuk 05 Feb '09

05 Feb '09

Hello all I want to get Co2MnO4 atoms.inp. I know that Co2MnO4 is a spinel structure, however I dont know the position of each atom in unit cell. If anyone knows that, please answer me... _________________________________________________________________ 간편하고 정확한 나만의 맞춤 검색, Live Search! http://search.live.com

2 2

An additional beta tester
by Scott Calvin 05 Feb '09

05 Feb '09

Hi Kathy, I just got a late volunteer for beta testing, whom I think will be a good addition: Ryan Hinrichs, professor of Chemistry at Drew University. Knows a little bit about XAFS, partially from collaboration with me, but has never used it himself. E-mail: Hinrich(a)drew.edu (Yes, his name ends in an "s" but his e-mail address does not.) --Scott

1 1

Possible solution to trouble in artemis analysis
by Kleper Oliveira Rocha 05 Feb '09

05 Feb '09

Dear all, Recentilly I post a massage about trouble with analysis in artemis. Well, I think that find the solution. In Portuguese some words are write with symbols like: fam*í*lia (family), prepara*ÇÃ*o (preparation) that are not accept by IFFEFIT programs. In the basis of the instalation of Windows XP in my computer and some folders had this symbols and this caused the trouble in Athena and Artemis. Thanks for all for the help. -- Kleper de Oliveira Rocha Doutorando em Engenharia Química Departamento de Engenharia Química/UFSCar Tels. 55 016 3351-8694

2 1

Lost second shell
by Eugenio Otal 04 Feb '09

04 Feb '09

Dear Carlo, with changes in function of time, you mean that repetitions of the spectra in the same sample are different from the firs to the last? What does this indicates? Thanks for you help, euG

2 1

Artemis parameter
by abhijeet gaur 04 Feb '09

04 Feb '09

Hi Scott, I know that alpha is not a temperature expansion coefficient .I guess it is a volume expansion coefficient( tell me if I am right). Actually I want to know that is it necessary to fit Ei, 3rd, 4th, cumulant in the fitting procedure .If yes then please tell me how to get them involve in the fit .when I give parameter like guess 3rd, guess 4th . Artemis dont take them . And about Ei I am completely blank.I dont know how to use itand from where i will get it. One more thing is that I am fitting Cu foil, CuO and Cu2O , so how many number of paths should I take . And Thanks a lot for your suggestions With regards Abhijeet

1 0