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

Correction to radial distance
by Francisco Garcia 24 May '13

24 May '13

Dear all, Can an experienced user kindly explain how to obtain the phase shift correction to the radial distance corresponding to FFT(chi(k)). From my chi(k) computation, I have several feff*.dat files (feff0001.dat, feff0002.dat,...............,feff00128.dat) because I have 128 paths. How do I use this information and IFEFFIT to compute the shifted spectrum? Thank you.

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JFEFF/FEFF9 "Save&Run" no longer works after Java Update -- FEFFgroup announcement
by Kevin Jorissen 16 May '13

16 May '13

Dear iFEFFIT community, a short update from the FEFF developers team: A recent Java update (Java 7 Update 21) broke some functionality of the JFEFF interface for the FEFF program. Users who update to J7U21 have noticed that when they click "Save&Run" nothing happens: the FEFF programs do not run and there is no output. We think this issue will affect people on all Operating Systems. To fix this issue there are two possibilities: * Roll back Java to a previous version. For security reasons please have at least Java 7 Update 11, which was an important security update, or newer. Instructions for rolling back Java can be found online. * We have updated JFEFF to work with the latest Java. This latest (J)FEFF version is not yet available on the official download website, but FEFF users with a valid license can contact us and we will provide them with a download link for the latest (J)FEFF. Please contact us directly. Users who currently have FEFF8 can upgrade to FEFF9 at any time at a discounted rate. Thank you to Linda Lim for her earlier post on the iFEFFIT ML. Cheers, Kevin Jorissen FEFFgroup - University of Washington

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normalization methods
by Matt Newville 16 May '13

16 May '13

Hi Folks, Over on the github pages for larch, Mauro and Bruce raised an issue about the "flattening" in Athena. See https://github.com/xraypy/xraylarch/issues/44 I've added a "flattened output" from Larch's pre_edge() function, but the question has been raised of whether this is "better" than the simpler normalized spectra, especially for doing PCA and/or LCF for XANES. Currently, the "normalized" spectra is just "(mu - pre_edge_line)/edge_step". Clearly, a line fitted to the pre-edge of the spectra is not sufficient to remove all instrumental backgrounds. In some sense, flattening attempts to do a better job, fitting the post-edge spectra to a quadratic function. As Mauro, Bruce, and Carmelo have pointed out, it is less clear that it is actually better for XANES analysis. I think the main concerns are that a) it is so spectra-specific, and b) it turns on at E0 with a step function. Bruce suggested doing something more like MBACK or Ifeffit's bkg_cl(). It would certainly be possible to do some sort of "flattening" so that mu follows the expected energy dependence from tabularized mu(E). Does anyone else have suggestions, opinions, etc? Feel free to give them here or at the github page.... --Matt

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Re: [Ifeffit] normalization methods
by Zack Gainsforth 15 May '13

15 May '13

Hi All, We did an analysis comparing on order of 100 XANES spectra and found that a normalization producing the most stereotypically "correct" spectrum did not always produce the best linear combinations between them. That is, we tend to think a XANES spectrum should be flat (derivative=0) before the edge, and then there is a step, and wiggles, and the wiggles are centered around another flat line. Certainly, this form of spectrum communicates well in publications, and probably it is best for publications given that different researchers use different normalization algorithms. However, when comparing XANES spectra against each other quantitatively, it is more important that the subtraction method be the same. What we did that worked well was write a normalization routine in MATLAB (derived from Matthew Marcus' description since we acquired XANES on his beamline). Then we were better able to compare spectra and fit them against each other using linear combination. When using spectra that were individually normalized, the linear combinations were never as good. Incidentally, this is an argument for always including raw spectra in supplementary materials even though you would want to use the normalized spectrum in a publication. Cheers, Zack On May 15, 2013, at 9:58 AM, ifeffit-request(a)millenia.cars.aps.anl.gov wrote: Send Ifeffit mailing list submissions to ifeffit(a)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(a)millenia.cars.aps.anl.gov You can reach the person managing the list at ifeffit-owner(a)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. normalization methods (Matt Newville) 2. Re: normalization methods (Matthew Marcus) 3. Re: normalization methods (Matt Newville) 4. Re: normalization methods (Matthew Marcus) 5. Re: normalization methods (George Sterbinsky) ---------------------------------------------------------------------- Message: 1 Date: Wed, 15 May 2013 09:35:41 -0500 From: Matt Newville <newville(a)cars.uchicago.edu> To: XAFS Analysis using Ifeffit <ifeffit(a)millenia.cars.aps.anl.gov> Subject: [Ifeffit] normalization methods Message-ID: <CA+7ESboBg5uOS6or-TurJy9zPGhoA73c+bErNkWsuO4GC4Cpug(a)mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Hi Folks, Over on the github pages for larch, Mauro and Bruce raised an issue about the "flattening" in Athena. See https://github.com/xraypy/xraylarch/issues/44 I've added a "flattened output" from Larch's pre_edge() function, but the question has been raised of whether this is "better" than the simpler normalized spectra, especially for doing PCA and/or LCF for XANES. Currently, the "normalized" spectra is just "(mu - pre_edge_line)/edge_step". Clearly, a line fitted to the pre-edge of the spectra is not sufficient to remove all instrumental backgrounds. In some sense, flattening attempts to do a better job, fitting the post-edge spectra to a quadratic function. As Mauro, Bruce, and Carmelo have pointed out, it is less clear that it is actually better for XANES analysis. I think the main concerns are that a) it is so spectra-specific, and b) it turns on at E0 with a step function. Bruce suggested doing something more like MBACK or Ifeffit's bkg_cl(). It would certainly be possible to do some sort of "flattening" so that mu follows the expected energy dependence from tabularized mu(E). Does anyone else have suggestions, opinions, etc? Feel free to give them here or at the github page.... --Matt ------------------------------ Message: 2 Date: Wed, 15 May 2013 07:57:14 -0700 From: Matthew Marcus <mamarcus(a)lbl.gov> To: XAFS Analysis using Ifeffit <ifeffit(a)millenia.cars.aps.anl.gov> Subject: Re: [Ifeffit] normalization methods Message-ID: <5193A24A.5090506(a)lbl.gov> Content-Type: text/plain; charset=ISO-8859-1; format=flowed What I typically do for XANES is divide mu-mu_pre_edge_line by a linear function which goes through the post-edge oscillations. This division goes over the whole data range, including pre-edge. If the data has obvious curvature in the post-edge, I'll use a higher-order polynomial. For transmission data, what sometimes linearizes the background is to change the abscissa to 1/E^2.7 (the rule-of-thumb absorption shape) and change it back afterward. All this is, of course, highly subjective and one of the reasons for taking extended XANES data (300eV, for instance). For short-range XANES, there isn't enough info to do more than divide by a constant. Once this is done, my LCF programs allow a slope adjustment as a free parameter, thus muNorm(E) = (1+a*(E-E0))*Sum_on_ref{x[ref]*muNorm[ref](E)}. A sign that this degree of freedom may be being abused is if the sum of the x[ref] is far from 1 or if a*(Emax-E0) is large. Don't get me started on overabsorption :-) mam On 5/15/2013 7:35 AM, Matt Newville wrote: > Hi Folks, > > Over on the github pages for larch, Mauro and Bruce raised an issue > about the "flattening" in Athena. See > https://github.com/xraypy/xraylarch/issues/44 > > I've added a "flattened output" from Larch's pre_edge() function, but > the question has been raised of whether this is "better" than the > simpler normalized spectra, especially for doing PCA and/or LCF for > XANES. > > Currently, the "normalized" spectra is just "(mu - > pre_edge_line)/edge_step". Clearly, a line fitted to the pre-edge of > the spectra is not sufficient to remove all instrumental backgrounds. > In some sense, flattening attempts to do a better job, fitting the > post-edge spectra to a quadratic function. As Mauro, Bruce, and > Carmelo have pointed out, it is less clear that it is actually better > for XANES analysis. I think the main concerns are that a) it is so > spectra-specific, and b) it turns on at E0 with a step function. > > Bruce suggested doing something more like MBACK or Ifeffit's bkg_cl(). > It would certainly be possible to do some sort of "flattening" so > that mu follows the expected energy dependence from tabularized mu(E). > > Does anyone else have suggestions, opinions, etc? Feel free to give > them here or at the github page.... > > --Matt > _______________________________________________ > Ifeffit mailing list > Ifeffit(a)millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > ------------------------------ Message: 3 Date: Wed, 15 May 2013 10:25:23 -0500 From: Matt Newville <newville(a)cars.uchicago.edu> To: XAFS Analysis using Ifeffit <ifeffit(a)millenia.cars.aps.anl.gov> Subject: Re: [Ifeffit] normalization methods Message-ID: <CA+7ESbrhv1WHj8r2v1-U7wurQCvZnmFjrmAf9HNbTfcRjFn77Q(a)mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1 Hi Matthew, On Wed, May 15, 2013 at 9:57 AM, Matthew Marcus <mamarcus(a)lbl.gov> wrote: > What I typically do for XANES is divide mu-mu_pre_edge_line by a linear > function which goes through the post-edge oscillations. > This division goes over the whole data range, including pre-edge. If the > data has obvious curvature in the post-edge, I'll use a higher-order > polynomial. For transmission data, what sometimes linearizes the background > is to change the abscissa to 1/E^2.7 (the rule-of-thumb absorption > shape) and change it back afterward. All this is, of course, highly > subjective and one of the reasons for taking extended XANES data (300eV, > for instance). For short-range XANES, there isn't enough info to do more > than divide by a constant. Once this is done, my LCF programs allow > a slope adjustment as a free parameter, thus muNorm(E) = > (1+a*(E-E0))*Sum_on_ref{x[ref]*muNorm[ref](E)}. A sign that this degree of > freedom > may be being abused is if the sum of the x[ref] is far from 1 or if > a*(Emax-E0) is large. Don't get me started on overabsorption :-) > mam Thanks -- I should have said that pre_edge() can now do a victoreen-ish fit, regressing a line to mu*E^nvict (nvict can be any real value). Still, it seems that the current flattening is somewhere between "better" and "worse", which is unsettling... Applying the "flattening" polynomial to the pre-edge range definitely seems to give poor results, but maybe some energy-dependent compromise is possible. And, of course, over-absorption is next on the list! --Matt ------------------------------ Message: 4 Date: Wed, 15 May 2013 08:41:55 -0700 From: Matthew Marcus <mamarcus(a)lbl.gov> To: XAFS Analysis using Ifeffit <ifeffit(a)millenia.cars.aps.anl.gov> Subject: Re: [Ifeffit] normalization methods Message-ID: <5193ACC3.3090007(a)lbl.gov> Content-Type: text/plain; charset=ISO-8859-1; format=flowed The way I commonly do pre-edge is to fit with some form plus a power-law singularity representing the initial rise of the edge, then subtract out that "some form". Now, that form can be either linear, linear+E^(-2.7) (for transmission), or linear+ another power-law singularity centered at the center passband energy of the fluorescence detector. That latter is for fluorescence data which is affected by the tail of the elastic/Compton peak from the incident energy. Whichever form is taken gets subtraccted from the whole data range, resulting in data which is pre-edge-subtracted but not yet post-edge normalized. The path then splits; for EXAFS, the usual conversion to k-space, spline fitting in the post-edge, subtraction and division is done, all interactively. Tensioned spline is also available due to request of a prominent user. For XANES, the post-edge is fit as previously described. Thus, there's no distinction made between data above and below E0 in XANES, whereas there is such a distinction in EXAFS. mam On 5/15/2013 8:25 AM, Matt Newville wrote: > Hi Matthew, > > On Wed, May 15, 2013 at 9:57 AM, Matthew Marcus <mamarcus(a)lbl.gov> wrote: >> What I typically do for XANES is divide mu-mu_pre_edge_line by a linear >> function which goes through the post-edge oscillations. >> This division goes over the whole data range, including pre-edge. If the >> data has obvious curvature in the post-edge, I'll use a higher-order >> polynomial. For transmission data, what sometimes linearizes the background >> is to change the abscissa to 1/E^2.7 (the rule-of-thumb absorption >> shape) and change it back afterward. All this is, of course, highly >> subjective and one of the reasons for taking extended XANES data (300eV, >> for instance). For short-range XANES, there isn't enough info to do more >> than divide by a constant. Once this is done, my LCF programs allow >> a slope adjustment as a free parameter, thus muNorm(E) = >> (1+a*(E-E0))*Sum_on_ref{x[ref]*muNorm[ref](E)}. A sign that this degree of >> freedom >> may be being abused is if the sum of the x[ref] is far from 1 or if >> a*(Emax-E0) is large. Don't get me started on overabsorption :-) >> mam > > Thanks -- I should have said that pre_edge() can now do a > victoreen-ish fit, regressing a line to mu*E^nvict (nvict can be any > real value). > > Still, it seems that the current flattening is somewhere between > "better" and "worse", which is unsettling... Applying the > "flattening" polynomial to the pre-edge range definitely seems to give > poor results, but maybe some energy-dependent compromise is possible. > > And, of course, over-absorption is next on the list! > > --Matt > _______________________________________________ > Ifeffit mailing list > Ifeffit(a)millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > ------------------------------ Message: 5 Date: Wed, 15 May 2013 12:58:53 -0400 From: George Sterbinsky <GeorgeSterbinsky(a)u.northwestern.edu> To: XAFS Analysis using Ifeffit <ifeffit(a)millenia.cars.aps.anl.gov> Subject: Re: [Ifeffit] normalization methods Message-ID: <CALoY8YzRCAa3w=8hC=Pn50cysiaVzYR6GrRCZDnW9d2gvPg7Gw(a)mail.gmail.com> Content-Type: text/plain; charset="iso-8859-1" The question of whether it is appropriate to use flattened data for quantitative analysis is something I've been thinking about a lot recently. In my specific case, I am analyzing XMCD data at the Co L-edge. To obtain the XMCD, I measure XAS with total electron yield detection using a ~70% left or right circularly polarized beam and flip the magnetic field on the sample at every data point. The goal then, is to subtract the XAS measured in a positive field (p-XAS) from XAS measured in a negative field (n-XAS) and get something (the XMCD) that is zero in the pre-edge and post-edge regions. I often find that after removal of a linear pre-edge, the spectra still have a linearly increasing post edge (with EXAFS oscillations superimposed on it), and the slope of the n-XAS and p-XAS post-edge lines are different. In this case simply multiplying the n-XAS and p-XAS by constants will never give an XMCD spectrum that is zero in the post edge region. There is then some component of the XAS background that is not accounted for by linear subtraction and multiplication by a constant. It seems to me that flattening could be a good way to account for such a background. So is flattening a reasonable thing to do in a case such as this, or is there a better way to account for such a background? Thanks, George On Wed, May 15, 2013 at 11:41 AM, Matthew Marcus <mamarcus(a)lbl.gov> wrote: > The way I commonly do pre-edge is to fit with some form plus a power-law > singularity representing the initial rise of the edge, then > subtract out that "some form". Now, that form can be either linear, > linear+E^(-2.7) (for transmission), or linear+ another power-law > singularity centered at the center passband energy of the fluorescence > detector. That latter is for fluorescence data which is affected by > the tail of the elastic/Compton peak from the incident energy. Whichever > form is taken gets subtraccted from the whole data range, resulting > in data which is pre-edge-subtracted but not yet post-edge normalized. > The path then splits; for EXAFS, the usual conversion to k-space, spline > fitting in the post-edge, subtraction and division is done, all > interactively. Tensioned spline is also available due to request of a > prominent user. > For XANES, the post-edge is fit as previously described. Thus, there's no > distinction made between data above and below E0 in XANES, whereas > there is such a distinction in EXAFS. > mam > > > On 5/15/2013 8:25 AM, Matt Newville wrote: > >> Hi Matthew, >> >> On Wed, May 15, 2013 at 9:57 AM, Matthew Marcus <mamarcus(a)lbl.gov> wrote: >> >>> What I typically do for XANES is divide mu-mu_pre_edge_line by a linear >>> function which goes through the post-edge oscillations. >>> This division goes over the whole data range, including pre-edge. If the >>> data has obvious curvature in the post-edge, I'll use a higher-order >>> polynomial. For transmission data, what sometimes linearizes the >>> background >>> is to change the abscissa to 1/E^2.7 (the rule-of-thumb absorption >>> shape) and change it back afterward. All this is, of course, highly >>> subjective and one of the reasons for taking extended XANES data (300eV, >>> for instance). For short-range XANES, there isn't enough info to do more >>> than divide by a constant. Once this is done, my LCF programs allow >>> a slope adjustment as a free parameter, thus muNorm(E) = >>> (1+a*(E-E0))*Sum_on_ref{x[ref]***muNorm[ref](E)}. A sign that this >>> degree of >>> freedom >>> may be being abused is if the sum of the x[ref] is far from 1 or if >>> a*(Emax-E0) is large. Don't get me started on overabsorption :-) >>> mam >>> >> >> Thanks -- I should have said that pre_edge() can now do a >> victoreen-ish fit, regressing a line to mu*E^nvict (nvict can be any >> real value). >> >> Still, it seems that the current flattening is somewhere between >> "better" and "worse", which is unsettling... Applying the >> "flattening" polynomial to the pre-edge range definitely seems to give >> poor results, but maybe some energy-dependent compromise is possible. >> >> And, of course, over-absorption is next on the list! >> >> --Matt >> ______________________________**_________________ >> Ifeffit mailing list >> Ifeffit(a)millenia.cars.aps.anl.**gov <Ifeffit(a)millenia.cars.aps.anl.gov> >> http://millenia.cars.aps.anl.**gov/mailman/listinfo/ifeffit<http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit> >> >> ______________________________**_________________ > Ifeffit mailing list > Ifeffit(a)millenia.cars.aps.anl.**gov <Ifeffit(a)millenia.cars.aps.anl.gov> > http://millenia.cars.aps.anl.**gov/mailman/listinfo/ifeffit<http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit> >

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problem with importing data between version of artemis
by Georges Siddiqi 14 May '13

14 May '13

Hi All, I've done a fit in the old version of Artemis (0.8.014), and wanted to import this fit into the new version of artemis (demeter 0.9.15) that I have to play around with it a bit more. The problem is, when I import the the "old-style artemis project", and do the same fit, the values, and fit itself are nowhere near similar to what i got with the old version of Artemis. what is the cause of this discrepancy? As far as I can tell from double checking all the fitting parameters, windows, variables, etc, they are all exactly the same. Even if I try to just do a summation in the new version with my best-fit values from the old version, the fit is completely different. Previously when I was importing fits between versions I had no issues whatsoever. I've attached the artemis project file (W EXAFS.apj) that gives me a good fit in the old version, and a poor fit in the new version. thanks, georges

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Athena- Demeter 0.9.14 importing data
by Atul Bansode 13 May '13

13 May '13

Hi All, I am using Athena (Demeter 0.9.14) to process the EXAFS data of Copper samples. Athena reads the data correctly however my problem is concerned with the importing the data. When I import the data, in the Athena: Column Selection dialog box the Energy units is shown in keV by default. Since my data is in eV, I can always change the keV to eV and work when it's a single file. My problem starts when I try to import multiple files where I choose Energy units as eV in the dialog box however this setting gets applied to the first file only. Remaining data files are read as keV which creates a problem for me to process the data. Is there any way to apply same Energy units to all the files while they are getting imported ? Or is it possible to change the Energy units after importing files ? I appreciate all your help. Thanks in advance ! Best regards Atul

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Installing on Mac OSX Lion
by Nate Turner 10 May '13

10 May '13

Hello, I believe I have successfully installed PGPLOT, Ifeffit, and the horae suite of programs onto my mac OSX and have constructed executable files for artemis, athena, atoms, and hephaestus. I am now at a loss however, as when I try to run them they fail and say they are looking for _iff_exec. Is this part of the Ifeffit program? After I built Ifeffit, I can't seem to find any executable file that opens Ifeffit. Did I not successfully install Ifeffit? Also, what is the purpose of iXAFS program for Mac OS X? when I run it I am asked to direct the program to the data files and there is a button for each of the horae suite programs but they don't launch anything. I am very lost by all this and would appreciate the help. Thank you, Nate Turner Graduate Student Washington State University

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NiO2 XAS data
by Mehmet Nurullah Ates 07 May '13

07 May '13

Dear all; I am a grad student and my research is about investigation on advanced cathode active materials for lithium ion batteries. We need NiO2 (Ni4+) XAS data if you could provide us. I know couple websites that can allow us to download Ni3+ Ni2+ but could not find for the Ni4+. If you have any Ni4+ XAS data, we will appreciate for receiving the data, if not you can direct me to any website or person that I can acquire. Thanks a lot Best -- Mehmet Nurullah Ates Northeastern University-PhD Candidate Center for Renewable Energy Technology 317 Egan Research Center 360 Huntington Ave. Boston, MA 02115 617-373-5630 (Phone) 617-373-8949 (Fax)

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Problem with running Demeter
by Amitava D Roy 02 May '13

02 May '13

Hi Matt/Alexander/Chris, Thanks for all the suggestions. The fix wasn't as drastic as re-installation of the operating system, system restore on Windows 7 did the job. What I did was quite stupid. I will be more careful next time. Thanks, Amitava Amitava Roy J. Bennett Johnston, Sr., Center for Advanced Microstructures and Devices (CAMD) Louisiana State University, Baton Rouge, LA 70806

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Re: [Ifeffit] Problem with running Demeter
by Alexander Riskin 02 May '13

02 May '13

Dear Amativa, Bruce is right, Ccleaner messed up your system and, unfortunately, beyond repair. Ccleaner promises indeed to remove unused DLL's from your system but is very bad at guessing which DLL's are really obsolete and has a tendency to assume DLL's are unused instead of playing it safe. Therefore, this piece of software needs to be handled by an expert hand, or you butcher your system as you seem to have done. I know this because I made the exact same mistake 16 years ago after which my windows 98 didn't even boot up anymore, so I'm even surprised your pc is still running. The solution to this problem? Complete reinstallation of your OS, trying to manually repair is very complicated and time consuming. You will probably run into similar problems with other applications as well because of missing DLL's. regards, Alexander -- dr. ir. Alexander Riskin Doctor-Navorser IMO - Inorganic and Physical Chemistry T +32(0)11 26 83 94 | F +32(0)11 26 83 23 http://www.uhasselt.be Universiteit Hasselt | Campus Diepenbeek Agoralaan Gebouw D | B-3590 Diepenbeek Kantoor G1.94

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