October 2004 - Ifeffit - millenia.cars.aps.anl.gov

re:fits
by k-kupiecki＠northwestern.edu 15 Jan '05

15 Jan '05

Thank you Bruce and Shelley! I just wanted to thank Matt, Bruce and everyone involved with IFEFFIT/Artemis/Athena... it has been a Godsend.... I couldn't have stumbled on it at a better time (I'm frantically trying to analyze about 4 beamtimes worth of SEXAFS data for papers and my thesis and WINXAS wasn't really working out for me)!!!!! Does anyone have any suggestions for additional literature in regards to better understanding the quality of fits and the parameters involved?.... or perhaps know when we might be able to expect a updated version of the Artemis literature? (What is currently there has helped me sooo much that I've been checking for an update every couple of weeks hoping to get see sections 2.2-3.2..... ) Also.... I guess I've realized that only knowing IFEFFIT with Artemis I kinda take things for granted (like I didn't know that IFEFFIT was having problems, in certain cases since I had only been checking the "Results" and the error messages on the bottom of the window....) which meant I missed errors like this in the IFEFFIT (since I didn't notice anything unusual in the "Results"): ............ # Do the fit! ## fitting difference of Cov_0_06ML_bl1435_111703.chi and one or more paths ... ## === data set #1 of 1 feffit(1-8, group=data0_fit, chi=data0.chi, k=data0.k, kweight=2.00, rmin=1, rmax=4, kmin=2.5, kmax=15, dk=2, kwindow=kaiser-bessel, fit_space=R, do_bkg=no, data_set=1, data_total=1) feffit fitting 1 data sets fitting ... fitting ... fitting ... fitting ... fitting ... fitting ... fitting ... fitting ... no uncertainties estimated! fit gave a warning message: too many fit iterations. try again with better guesses or a simpler problem. ............................................... I guess my question is.... is there anything else I should be looking for in the IFEFFIT printout that I might not otherwise notice by just using Artemis and looking at the error messages and "Results"? Thanks for the input! Sincerely, Kristine Witkowski Northwestern University

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Athena & Artemis in Windows
by Peter Southon 22 Dec '04

22 Dec '04

Hello Windows people A few days ago Shelly suggested that Athena and Artemis don't work when installed in the directory "C:/program files/ifeffit/". This has always worked for me using XP, though I wouldn't be surprised if it caused problems in some earlier versions of Windows. Regarding Poorani's question about TRAP files, I have found it useful to put a shortcut to "C:/program files/ifeffit/horae/stash/ARTEMIS.TRAP" on my desktop or wherever for easy access. Cheers, Peter >Date: Fri, 11 Jun 2004 08:36:32 -0500 >From: "Kelly, Shelly D." <SKelly(a)anl.gov> >Subject: RE: [Ifeffit] Running FEFF >To: "XAFS Analysis using Ifeffit" <ifeffit(a)millenia.cars.aps.anl.gov> >Message-ID: <1C1577844A0BDF448E14E8CCB2F74424015A1B6D(a)ANLMAIL.anl.gov> >Content-Type: text/plain; charset="us-ascii" > >Hi Poorani, > >I believe that Athena and Artemis do not work properly when installed in >the C:/program files/ifeffit directory. The installation proceedures >say to specify C:/ifeffit instead. To fix if, but all of C:/program >files/ifeffit into the trash and then re-install. > >Shelly Peter Southon Post Doctoral Fellow School of Chemistry University of Sydney NSW 2006, Australia +61 2 9351 4425

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RE: [Ifeffit] Using more than one E0
by Kelly, Shelly D. 15 Dec '04

15 Dec '04

Hi Guys, I wanted to add another comment about using multiple E0's. One of the best formulas that I have found involves assigning different atom types different E0's. This method seems to work well for M.S. paths. Here is an example of how it goes. I think that Daniel Haskel was the first to publish this type of E0 stuff. "Single and multiple scattering XAFS in BaZrO3: a comparison between theory and experiment" D. Haskel, B. Ravel, M. Newville and E. A. Stern Physica B 208&209 (1995) 151 Lets pretend that we have a copper oxide that we want to model. First shell Oxygen called O1, Second shell Cu called Cu1, Third shell Oxygen called O2. This method would use three E0's. One for the first shell oxygen atoms, Eo1. One for all the Cu atoms Ecu. and one for all other oxygen atoms Eo2. The Cu-O1 path has E0=Eo1. The Cu-Cu1 path has E0=Ecu. The Cu-O2 path has E0=Eo2. The Cu-O1-Cu-O1 path has E0=Eo1, (only scattering from O1 atom). The Cu-O1-Cu1-Cu path has E0=0.5*Eo1+0.5*Ecu. (scattering once from O1 and once from Cu1) ... And so forth and so on. Now if you set something like this up. You need to look at the results carefully and see if it works. Generally, scattering from an atom that has lost an electron due to an ionic bond will have a positive deltaE, and scattering from an atom that has gained an electron will have a negative deltaE. Of course this negative/positive deltaE is added to the alignment deltaE. If the values for Eo2 and Ecu are the same within the uncertainties of the measurement then you need to make them the same variable, so then you will only have two energy shifts, but you can still use it. This is most often the case as Matt mentioned but I always like to test it out. In addition, one electron transfer is about a shift by 6 eV, so if these values differ by more than say 10 eV something is not right. Since the shift is generally smallish, say 2 eV, your fit has to be really accurate to "see" these shifts. In particular they seem to be most important when you have all the deltaR values constrained in some way so that the error in deltaR is really really small. For example all deltaR values are related to unit cell parameters and atomic positions or and overall expansion term. HTH Shelly -----Original Message----- From: Wojciech Gawelda [mailto:wojciech.gawelda@epfl.ch] Sent: Thursday, May 27, 2004 1:18 PM To: ifeffit(a)millenia.cars.aps.anl.gov Subject: [Ifeffit] Using more than one E0 Hi everybody, I would like to address a couple of questions which are partially related to my recent struggles in fitting some EXAFS data. I'm trying to fit my data using several shells of different neighbors including a few single scattering paths and also so multiple scattering contributions (mainly collinear multiple scattering paths) all calculated with the help of FEFF 8.20. Now, I found once in the FEFFIT manual the following suggestion: one might consider using several different E0's for different paths in order to improve the fit. Ok, the explanation was based on some approximations coming from FEFF code which include incomplete core-hole shielding, lack of angular variations of the valence charge distribution and charge transfer between atoms in polar materials. My question is the following: does anyone of you have some experience with such procedure? And if yes, shall than distinguish between the first shell of nearest neighbors and the rest of the atoms in terms of their E0 corrections (using 2 parameters)? Or perhaps one can use separate E0's for each path? That's one thing... The second question concerns the background correction in Artemis: I was trying to find an easy explanation of what this procedure does during the fit but I guess I'm still somewhat confused...how one can judge whether the spline co-refinement does the right job? Some people on this mailing list underline that one should avoid high correlations between fitting parameters and background parameters in order to make sure that the fit is correct. But is it the only criterion? In some of my fits background line looks kind of constant over the entire R-range which was taken into the fit. Sometimes it becomes like a modulation peaking underneath some scattering paths...even if the background parameters don't correlate significantly with fitting parameters I have my doubts whether the result is trustful. Any hints about this procedure? Well, I'll greatly appreciate any comments and feedback from all you guys. I hope I'll be able to share some of my own soon :-) Cheers, Wojciech ********************************************************************* Wojciech Gawelda Laboratoire de Spectroscopie Ultrarapide (LSU) Institut des Sciences et Ingénierie Chimiques (ISIC), Faculté des Sciences de Base (SB-BSP) Ecole Polytechnique Fédérale de Lausanne (EPFL) CH-1015 Lausanne-Dorigny, Switzerland Tel.: +41 (21) 693 0452 Fax.: +41 (21) 693 0422 E-mail: <mailto:wojciech.gawelda@epfl.ch> wojciech.gawelda(a)epfl.ch WWW: <http://lsu.epfl.ch> http://lsu.epfl.ch *********************************************************************

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Fitting Commercial Molybdenum Disulfide
by dmc＠pdx.edu 04 Nov '04

04 Nov '04

Hi Mailing list, I'm back at fitting commercial Molybdenum Disulfide to a Hexagonal p 63/m m c space group. Although my present fit is reasonable, thanks to the mailing list in August, I was hoping someone might have more suggestions to optimize it. Also, in order to better my fit, I still have seperate e0's, one for the first path, one for the remaining 2 paths. I haven't gotten a satisfactory physical explanation for this and I thought someone might have a good one. Also, the data on the same sample from two different beamlines seems to be somewhat different, namely the Reduced chi-square is very different (75.6 in one, 636.4 in the other). In both cases I use the first 3 single scattering paths. I may have included too much info, but better too much than too little. Thank You, Dan Carter Here are my parameters in both cases, values differ somewhat: Set: Amp = 0.7 guess: eO ~ 1.57 (1.52) (used for first path) guess: eO_1 ~ -4.77 (2.43) (used for remaining 2 paths) guess: ss ~ 0.0027 (0.000427) guess: alpha ~ -0.004 (0.003255) (positive for second fit) delr_1: alpha*reff First Fit: Project title : Fitting merge 10_15_04.chi Comment : Prepared by : Contact : Started : 11:49:36 on 22 October, 2004 This fit at : 11:10:57 on 28 October, 2004 Environment : Artemis 0.7.010 using Windows 2000, perl 5.006001, Tk 800.024, and Ifeffit 1.2.6 ============================================================ Independent points = 14.312500000 Number of variables = 4.000000000 Chi-square = 779.303886008 Reduced Chi-square = 75.568861674 R-factor = 0.041210572 Measurement uncertainty (k) = 0.000827712 Measurement uncertainty (R) = 0.022111003 Number of data sets = 1.000000000 Guess parameters +/- uncertainties (initial guess): e0_1 = -4.7737110 +/- 2.4268840 (guessed as -4.773687 (2.426889)) ss = 0.0027360 +/- 0.0004270 (guessed as 0.002736 (0.000427)) e0 = 1.5684690 +/- 1.5209160 (guessed as 1.568507 (1.520918)) alpha = -0.0040060 +/- 0.0032550 (guessed as -0.004006 (0.003255)) Def parameters: delr_1 = -0.0158980 Set parameters: amp = 0.7 Correlations between variables: e0_1 and alpha --> 0.8622 e0 and alpha --> 0.7870 e0_1 and e0 --> 0.7064 All other correlations are below 0.25 Project title : Fitting merge 10_15_04.chi Comment : Prepared by : Contact : Started : 11:49:36 on 22 October, 2004 This fit at : 11:10:57 on 28 October, 2004 Environment : Artemis 0.7.010 using Windows 2000, perl 5.006001, Tk 800.024, and Ifeffit 1.2.6 ============================================================ Independent points = 14.312500000 Number of variables = 4.000000000 Chi-square = 779.303886008 Reduced Chi-square = 75.568861674 R-factor = 0.041210572 Measurement uncertainty (k) = 0.000827712 Measurement uncertainty (R) = 0.022111003 Number of data sets = 1.000000000 Guess parameters +/- uncertainties (initial guess): e0_1 = -4.7737110 +/- 2.4268840 (guessed as -4.773687 (2.426889)) ss = 0.0027360 +/- 0.0004270 (guessed as 0.002736 (0.000427)) e0 = 1.5684690 +/- 1.5209160 (guessed as 1.568507 (1.520918)) alpha = -0.0040060 +/- 0.0032550 (guessed as -0.004006 (0.003255)) Def parameters: delr_1 = -0.0158980 Set parameters: amp = 0.7 Correlations between variables: e0_1 and alpha --> 0.8622 e0 and alpha --> 0.7870 e0_1 and e0 --> 0.7064 All other correlations are below 0.25 ===== Data set >>merge 6_17_04.chi<< ======================================== file: C:\Ifeffit\horae\stash\artemis.project.3\chi_data\merge 6_17_04.chi title lines: Athena data file -- Athena version 0.8.032 Saving merge 6_17_04 (group=merge) as chi(k) . Element=Mo Edge=K Background parameters . E0=20007.492 Eshift=0.000 Rbkg=1.000 . Standard=None . Kweight=2.0 Edge step=0.749 . Fixed step=no Flatten=yes . Pre-edge range: [ -150.000 : -75.000 ] . Normalization range: [ 150.000 : 895.199 ] . Spline range: [ 0.952 : 995.207 ] Clamps: None/Strong Foreward FT parameters . Kweight=2 Window=kaiser-bessel Phase correction=no . k-range: [ 2.000 : 16.100 ] dk=0.00 Backward FT parameters . R-range: [ 1.000 : 3.000 ] . dR=0.00 Window=kaiser-bessel Plotting parameters . Multiplier=1 Y-offset=0.000 . Merge in k space of: ** C:/USERS/Dan2/raw data MoS2 6_17_04/MoS2.101 (mos2_101) ** C:/USERS/Dan2/raw data MoS2 6_17_04/MoS2.102 (mos2_102) ** C:/USERS/Dan2/raw data MoS2 6_17_04/MoS2.103 (mos2_103) ** C:/USERS/Dan2/raw data MoS2 6_17_04/MoS2.104 (mos2_104) k-range = 2.000 - 13.500 dk = 2.000 k-window = kaiser-bessel k-weight = 2 R-range = 1.000 - 3.000 dR = 0.100 R-window = kaiser-bessel fitting space = R background function = none phase correction = none R-factor for this data set = 0.74613 Second Fit: Project title : Fitting merge 10_15_04.chi Comment : Prepared by : Contact : Started : 11:49:36 on 22 October, 2004 This fit at : 11:23:36 on 28 October, 2004 Environment : Artemis 0.7.010 using Windows 2000, perl 5.006001, Tk 800.024, and Ifeffit 1.2.6 ============================================================ Independent points = 14.312500000 Number of variables = 4.000000000 Chi-square = 6562.747150466 Reduced Chi-square = 636.387602469 R-factor = 0.032979787 Measurement uncertainty (k) = 0.000181935 Measurement uncertainty (R) = 0.004860095 Number of data sets = 1.000000000 Guess parameters +/- uncertainties (initial guess): e0_1 = -4.0720090 +/- 1.9194040 (guessed as -4.773711 (2.426884)) ss = 0.0046360 +/- 0.0004110 (guessed as 0.002736 (0.000427)) e0 = 1.7659580 +/- 1.1543880 (guessed as 1.568469 (1.520916)) alpha = 0.0010900 +/- 0.0028430 (guessed as -0.004006 (0.003255)) Def parameters: delr_1 = 0.0043250 Set parameters: amp = 0.7 Correlations between variables: e0_1 and alpha --> 0.8416 e0 and alpha --> 0.8045 e0_1 and e0 --> 0.7141 All other correlations are below 0.25 ===== Data set >>merge 10_15_04.chi<< ======================================== file: C:\Ifeffit\horae\stash\artemis.project.3\chi_data\merge 10_15_04.chi title lines: Athena data file -- Athena version 0.8.032 Saving merge 6_17_04 (group=merge) as chi(k) . Element=Mo Edge=K Background parameters . E0=20007.492 Eshift=0.000 Rbkg=1.000 . Standard=None . Kweight=2.0 Edge step=0.749 . Fixed step=no Flatten=yes . Pre-edge range: [ -150.000 : -75.000 ] . Normalization range: [ 150.000 : 895.199 ] . Spline range: [ 0.952 : 995.207 ] Clamps: None/Strong Foreward FT parameters . Kweight=2 Window=kaiser-bessel Phase correction=no . k-range: [ 2.000 : 16.100 ] dk=0.00 Backward FT parameters . R-range: [ 1.000 : 3.000 ] . dR=0.00 Window=kaiser-bessel Plotting parameters . Multiplier=1 Y-offset=0.000 . Merge in k space of: ** C:/USERS/Dan2/raw data MoS2 6_17_04/MoS2.101 (mos2_101) ** C:/USERS/Dan2/raw data MoS2 6_17_04/MoS2.102 (mos2_102) ** C:/USERS/Dan2/raw data MoS2 6_17_04/MoS2.103 (mos2_103) ** C:/USERS/Dan2/raw data MoS2 6_17_04/MoS2.104 (mos2_104) k-range = 2.000 - 13.500 dk = 2.000 k-window = kaiser-bessel k-weight = 2 R-range = 1.000 - 3.000 dR = 0.100 R-window = kaiser-bessel fitting space = R background function = none phase correction = none R-factor for this data set = 0.71585 Paths used to fit Both Data Sets, degen, s02 the same. other values different: F1 p 63/m m c: feff0001.dat .. feff = C:\Ifeffit\horae\stash\artemis.project.3\data0.feff2\feff0001.dat id = reff= 2.4135, nlegs= 2, path= Mo<->S label = r = 2.416130 degen = 6.000000 s02 = 0.700000 e0 = 1.765958 dr = 0.002630 ss2 = 0.004636 F1 p 63/m m c: feff0002.dat .. feff = C:\Ifeffit\horae\stash\artemis.project.3\data0.feff2\feff0002.dat id = reff= 3.1500, nlegs= 2, path= Mo<->Mo label = r = 3.153433 degen = 6.000000 s02 = 0.700000 e0 = -4.072009 dr = 0.003433 ss2 = 0.004636 F1 p 63/m m c: feff0003.dat .. feff = C:\Ifeffit\horae\stash\artemis.project.3\data0.feff2\feff0003.dat id = reff= 3.9683, nlegs= 2, path= Mo<->S label = r = 3.972625 degen = 6.000000 s02 = 0.700000 e0 = -4.072009 dr = 0.004325 ss2 = 0.004636

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Problem exporting fit data with ARTEMIS
by Norbert Weiher 02 Nov '04

02 Nov '04

Dear Friends, I did a multi-dataset fit (9 data sets) and had the following problem: When trying to export all the fits to a single file (using save marked groups as), I got an empty file and artemis trapped a warning like the following. For sake of reproducing, I attached the file. My Tk version is the one which we should use (i.e. not the newest one) and saving just the experimental data in just the same fashion works... Any ideas why this happens? Regards, Norbert -- Error message follows -- Tk::Error: Can't call method "dispose" on unblessed reference at /usr/bin/artemi s line 7971. main::save_selected at /usr/bin/artemis line 7971 [\&main::save_selected,k] Tk callback for .menu1.menu.menu7 Tk::__ANON__ at /usr/lib/perl5/site_perl/5.8.0/i586-linux-thread-multi/Tk.pm li ne 228 Tk::Menu::Invoke at /usr/lib/perl5/site_perl/5.8.0/i586-linux-thread-multi/Tk/M enu.pm line 530 (command bound to event) main::__ANON__('Tk::Error: Can\'t call method "dispose" on unblessed ref erenc...') called at blib/lib/Tk.pm (autosplit into blib/lib/auto/Tk/Error.al) l ine 402 Tk::Error('MainWindow=HASH(0x953f240)','Can\'t call method "dispose" on unblessed reference at /usr/b...','main::save_selected at /usr/bin/artemis line 7971','[\&main::save_selected,k]','Tk callback for .menu1.menu.menu7','Tk::__ANO N__ at /usr/lib/perl5/site_perl/5.8.0/i586-linux-thr...','Tk::Menu::Invoke at /u sr/lib/perl5/site_perl/5.8.0/i586-linux...','(command bound to event)') called a t /usr/lib/perl5/site_perl/5.8.0/i586-linux-thread-multi/Tk.pm line 340 eval {...} called at /usr/lib/perl5/site_perl/5.8.0/i586-linux-thread-mu lti/Tk.pm line 340 Tk::MainLoop() called at /usr/bin/artemis line 1785 -- Dr. rer. nat. Norbert Weiher (weiher(a)chem.ethz.ch) Institute for Chemical and Bioengineering - ETH Hönggerberg HCI E 117 - 8093 Zürich - Phone: +41 1 63 3 48 32

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RE: [Ifeffit] Artimis
by Chen, Yongsheng 02 Nov '04

02 Nov '04

Hi Matt, I did encounter that "No absorbing atom (ipot=0) defined" error sometimes, but I run Artemis only after I have feff calculations done. By the way, I use FEFF8. Thanks everybody for your kind help. I am afraid I can not do more test now since I am leaving tomorrow for Argonne for more XAFS experiments. Will check back if the problem remains after I have tried what you have suggested. Have a good weekend. Yongsheng > ---------- > From: ifeffit-bounces(a)millenia.cars.aps.anl.gov on behalf of Matt Newville > Reply To: XAFS Analysis using Ifeffit > Sent: Friday, October 22, 2004 2:20 PM > To: ravel(a)phys.washington.edu; XAFS Analysis using Ifeffit > Subject: Re: [Ifeffit] Artimis > > Hi, > > > On Friday 22 October 2004 4:38 pm, Chen, Yongsheng wrote: > > > Thanks for your advices. I did edit my Feff.inp in Word, but did not have > > > any problems with the old version. > > > > It is certainly possible to do so, but you MUST be careful to save the > > file as text. Because it is so easy to forget and just save in > > whatever format Word decides to use, I always discourage people from > > using Word for that purpose. > > Actually, Feff6 (and ifeffit) handle Unix and Windows line endings > just fine, but do have a harder time with Mac line-endings. I'm > not sure I know how to fix this: As far as I can tell it's at the > level of the fortran's read() statement. Sorry. > > One thing that confuses me is that Feff6 *should* have reported a > Feff 6L.02 > Fatal Error: No absorbing atom (ipot=0) defined > > which could have been used as a clue that something went wrong. > I don't know how artemis checks if a feff run went OK. > > > Hey Mac users! Could someone suggest a simple editor that Yongsheng, > > a new Mac user, should consider for the task of editing the kinds of > > text files that Feff and similar programs work with? > > TextEdit can save file with Unix-style line endings, especially if > you set the default to using 'Plain text' in the Preferences menu. > > BBedit is a popular and very good editor for Mac OS X. > > --Matt > > _______________________________________________ > Ifeffit mailing list > Ifeffit(a)millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit > >

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RE: [Ifeffit] Fitting Commercial Molybdenum Disulfide
by Kelly, Shelly D. 29 Oct '04

29 Oct '04

Hi Dan, I would suggest using one ezero with three different delr values for these three paths. You are introducting only one more variable. delr and ezero are correlated so by constraining delr you need more ezero values or vise versa. Shelly > -----Original Message----- > From: dmc(a)pdx.edu [mailto:dmc@pdx.edu] > Sent: Friday, October 29, 2004 10:25 AM > To: XAFS Analysis using Ifeffit > Subject: Re: [Ifeffit] Fitting Commercial Molybdenum Disulfide > > > Mike & list, > > Where can I find a reasonable model for my delr terms, > if I do assume > that the bond angles are changing/there is no isotropic > expansion? Is there a > description somewhere in the archives that I could look at? > > Creating different sigma squared parameters for each > path did help the R- Factor somewhat, but not the reduced > chi. Here's some data: > > > Fit with seperate sigma's: > > Independent points = 14.312500000 > Number of variables = 6.000000000 > Chi-square = 5778.957783654 > Reduced Chi-square = 695.212966455 > R-factor = 0.029041008 > Measurement uncertainty (k) = 0.000181935 > Measurement uncertainty (R) = 0.004860095 > Number of data sets = 1.000000000 > > > Guess parameters +/- uncertainties (initial guess): > e0_1 = -4.0347670 +/- 2.9998980 > (guessed as -4.072009 > (1.919404)) > ss = 0.0042860 +/- 0.0005990 > (guessed as 0.004636 > (0.000411)) > e0 = 1.6770760 +/- 1.3230290 > (guessed as 1.765958 > (1.154388)) > alpha = 0.0009180 +/- 0.0034050 > (guessed as 0.001090 > (0.002843)) > ss2 = 0.0048160 +/- 0.0006910 (0.0000) > ss3 = 0.0225310 +/- 0.0657250 (0.0000) > Def parameters: > delr_1 = 0.0036440 > Set parameters: > amp = 0.7 > > > Correlations between variables: > e0_1 and alpha --> 0.8542 > e0 and alpha --> 0.8470 > e0_1 and e0 --> 0.7407 > e0_1 and ss3 --> 0.7060 > alpha and ss3 --> 0.4715 > ss2 and ss3 --> -0.4214 > e0_1 and ss2 --> -0.3892 > e0 and ss3 --> 0.3772 > alpha and ss2 --> -0.2680 > All other correlations are below 0.25 > > > > > > > > > Fit without (original): > > > Independent points = 14.312500000 > Number of variables = 4.000000000 > Chi-square = 6562.747150128 > Reduced Chi-square = 636.387602437 > R-factor = 0.032979787 > Measurement uncertainty (k) = 0.000181935 > Measurement uncertainty (R) = 0.004860095 > Number of data sets = 1.000000000 > > > Guess parameters +/- uncertainties (initial guess): > e0_1 = -4.0720130 +/- 1.9194050 > (guessed as -4.072009 > (1.919404)) > ss = 0.0046360 +/- 0.0004110 > (guessed as 0.004636 > (0.000411)) > e0 = 1.7659560 +/- 1.1543880 > (guessed as 1.765958 > (1.154388)) > alpha = 0.0010900 +/- 0.0028430 > (guessed as 0.001090 > (0.002843)) > > Def parameters: > delr_1 = 0.0043250 > > Set parameters: > amp = 0.7 > > > Correlations between variables: > e0_1 and alpha --> 0.8416 > e0 and alpha --> 0.8045 > e0_1 and e0 --> 0.7141 > All other correlations are below 0.25 > > > _______________________________________________ > Ifeffit mailing list > Ifeffit(a)millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listi> nfo/ifeffit >

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RE: [Ifeffit] Fitting Commercial Molybdenum Disulfide
by Kelly, Shelly D. 29 Oct '04

29 Oct '04

Hi Dan, Take a look at the fit in q-space with the model below. I suspect that you have left out important Multiple scattering paths that would cause a miss-fit to the data at low k values. To test for this, change the fit range to something like 4.0 1/Anstroms for k-min value, and try again. Shelly > -----Original Message----- > From: dmc(a)pdx.edu [mailto:dmc@pdx.edu] > Sent: Friday, October 29, 2004 11:03 AM > To: XAFS Analysis using Ifeffit > Subject: RE: [Ifeffit] Fitting Commercial Molybdenum Disulfide > > > Hi Shelly, > > I seperated the delr's with different alpha terms, but > Mike seems to think > that this is assuming isotropic expansion that isn't there. > Also, the reduced > chi-square has gone up 150 or so. > > delr# define: alpha# * reff > > > Thanks for the help, Dan > > > Results with 1 eO and differing delr's: > > Independent points = 14.312500000 > Number of variables = 7.000000000 > Chi-square = 6186.771083042 > Reduced Chi-square = 846.054165202 > R-factor = 0.031090393 > Measurement uncertainty (k) = 0.000181935 > Measurement uncertainty (R) = 0.004860095 > Number of data sets = 1.000000000 > > > Guess parameters +/- uncertainties (initial guess): > ss = 0.0042720 +/- 0.0006590 > (guessed as 0.004636 > (0.000411)) > e0 = 1.3293700 +/- 1.4673640 > (guessed as 1.765958 > (1.154388)) > alpha = -0.0001750 +/- 0.0040010 > (guessed as 0.001090 > (0.002843)) > ss2 = 0.0043180 +/- 0.0007370 (0.0000) > ss3 = 0.0072300 +/- 0.0164390 (0.0000) > alpha2 = 0.0076940 +/- 0.0027880 (0.0000) > alpha3 = -0.0512670 +/- 0.0232140 (0.0000) > > Def parameters: > delr_1 = -0.0006930 > delr_2 = 0.0305320 > delr_3 = -0.2034430 > > Set parameters: > amp = 0.7 > > > Correlations between variables: > e0 and alpha --> 0.8441 > ss3 and alpha2 --> 0.7651 > ss2 and alpha2 --> -0.6441 > e0 and alpha2 --> 0.5682 > ss2 and ss3 --> 0.4871 > alpha and alpha2 --> 0.4785 > ss3 and alpha3 --> 0.3825 > e0 and alpha3 --> -0.2743 > All other correlations are below 0.25 > > > > > > Original (2 e0s): > > > Independent points = 14.312500000 > Number of variables = 6.000000000 > Chi-square = 5778.957783654 > Reduced Chi-square = 695.212966455 > R-factor = 0.029041008 > Measurement uncertainty (k) = 0.000181935 > Measurement uncertainty (R) = 0.004860095 > Number of data sets = 1.000000000 > > > Guess parameters +/- uncertainties (initial guess): > e0_1 = -4.0347670 +/- 2.9998980 > (guessed as -4.072009 > (1.919404)) > ss = 0.0042860 +/- 0.0005990 > (guessed as 0.004636 > (0.000411)) > e0 = 1.6770760 +/- 1.3230290 > (guessed as 1.765958 > (1.154388)) > alpha = 0.0009180 +/- 0.0034050 > (guessed as 0.001090 > (0.002843)) > ss2 = 0.0048160 +/- 0.0006910 (0.0000) > ss3 = 0.0225310 +/- 0.0657250 (0.0000) > > Def parameters: > delr_1 = 0.0036440 > > Set parameters: > amp = 0.7 > > > Correlations between variables: > e0_1 and alpha --> 0.8542 > e0 and alpha --> 0.8470 > e0_1 and e0 --> 0.7407 > e0_1 and ss3 --> 0.7060 > alpha and ss3 --> 0.4715 > ss2 and ss3 --> -0.4214 > e0_1 and ss2 --> -0.3892 > e0 and ss3 --> 0.3772 > alpha and ss2 --> -0.2680 > All other correlations are below 0.25 > > > > > > _______________________________________________ > Ifeffit mailing list > Ifeffit(a)millenia.cars.aps.anl.gov > http://millenia.cars.aps.anl.gov/mailman/listi> nfo/ifeffit >

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to Gael Poirier
by Bruce Ravel 27 Oct '04

27 Oct '04

Hi folks, Recently Gael Poirier has been having a problem using Athena with some XANES data. For whatever reason, when I send mail to Gael it gets bounced back. But he seems to receive mail from the mailing list. Go figure. Sorry for filling up people mail boxes, but I am using the list to send this along... B =============================================================== Gael, Thanks for sending the data. It is now clear what went wrong. I recently made a change in how Athena tries to detect xanes data, that is data that does not extend very far into the extended region. The advantage of identifying data that is xanes and not exafs is that Athena then does not have to do a background removal, which saves a little bit of time doing chores like alignment and normalization. Sadly, you have uncovered a bug. That happens. Your bug is that the kmax for the fourier transform gets set to when the data are imported as xanes. Then Athena mistakenly aborts when it sees this, even though no FT will be performed. Oops! Fortunately there is an easy work-around. When you import the data, explicitly import them as mu(E) rather than xanes(E). The only draw-back of doing so is that Athena will do a background removal every time you change the normalization parameters. That's not a big loss. Thanks for pointing this out. I will certainly fix this in the next release. -- Bruce Ravel ----------------------------------- ravel(a)phys.washington.edu Code 6134, Building 3, Room 405 Naval Research Laboratory phone: (1) 202 767 2268 Washington DC 20375, USA fax: (1) 202 767 4642 NRL Synchrotron Radiation Consortium (NRL-SRC) Beamlines X11a, X11b, X23b National Synchrotron Light Source Brookhaven National Laboratory, Upton, NY 11973 My homepage: http://feff.phys.washington.edu/~ravel EXAFS software: http://feff.phys.washington.edu/~ravel/software/exafs/

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citing Artemis and Athena?
by k-kupiecki＠northwestern.edu 27 Oct '04

27 Oct '04

Hi everyone, I'm in the process of writing up my thesis and I've used Athena and Artemis quite a bit for the analysis of my SEXAFS data.... I was wondering what is the appropriate way to give references for this software and it's use? To my knowledge there are journal articles etc. regarding AUTOBK, FEFFIT, etc. Do I cite those? are there additional ways I should cite to give credit for Athena and Artemis too? Thanks for any suggestions you have! -Kristine Witkowski

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