problem with E0 (enot) parameters

Zajac, Dariusz A.

19 Jun 2009 19 Jun '09

9:33 a.m.

Hi all, can anybody help me and send some link about problems with enot in Artemis? in google, tutorials I couldn't find any help. Of course are few posts about delr or ss parameters, but enot is somehow omited (or I can not find it...) the problem is with fiting K4W(CN)8*2H2O at W:L3 edge. fit and others parameters looks ok, except enot for C and N, where both are around 12 and don't want to fit to other values... thanks darek ------------------------------------------------------------------------ dr. Zajac Dariusz A. Deutsches Elektronen-Synchrotron -Hasylab phone: +49-40-8998-2932 Notkestr. 85 fax: +49-40-8998-2787 22607 Hamburg e-mail: dariusz.zajac@desy.de Germany ------------------------------------------------------------------------

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Scott Calvin

19 Jun 19 Jun

10:22 a.m.

Hi Zajac, What happens if you constrain all E0's to be the same? In the fit where they come out large, what are the uncertainties in the E0's? What are their correlations with other fitted parameters? There has been some debate in this list on the past as to how useful it is to allow for different E0's for different paths. It may be that Artemis is shifting the E0's for those paths in lieu of some other correlated parameter. --Scott Calvin Sarah Lawrence College On Jun 19, 2009, at 5:33 AM, Zajac, Dariusz A. wrote:

...

Hi all, can anybody help me and send some link about problems with enot in Artemis? in google, tutorials I couldn't find any help. Of course are few posts about delr or ss parameters, but enot is somehow omited (or I can not find it...)

the problem is with fiting K4W(CN)8*2H2O at W:L3 edge. fit and others parameters looks ok, except enot for C and N, where both are around 12 and don't want to fit to other values... thanks darek

Zajac, Dariusz A.

11:30 a.m.

Hi Calvin, thanks for the email. I have tried to find something on mailing list about E0 but it seems that my "searching words" were not correct. I found only few posts but non of them explained (or followed) the problem with large enot. enot parameters are closed to eachother e.g. enot_C = 12.597(+-0.654) and enot_N=12.407(+-1.776); correlations e.g. enot_N and delr_N=0.744, enot_C and delr_C=0.605 enot_C and enot_N=-0.313 more detail you can find in the attachment or below. I have found that the value of the first background variable is large (-3437(+-23034)) when I constrain both enot's parameters I do not see huge changes in parameters, chi^2 enot, amp, delr and ssh are the same in the range of uncertainties. I agree with you that program can shift not the correct parameter, but why every time I change parameters (I shift parameters from the local minimum) their come back? cheers darek Independent points = 45.279296875 Number of variables = 30.000000000 Chi-square = 219223.767 Reduced Chi-square = 14347.765383235 R-factor = 0.022707172 Measurement uncertainty (k) = 0.000102780 Measurement uncertainty (R) = 0.000306293 Number of data sets = 1.000000000 Guess parameters +/- uncertainties (initial guess): amp = 0.8496050 +/- 0.0767160 (guessed as 0.849812 (0.095158)) enot_C = 12.5967170 +/- 0.6539780 (guessed as 12.601228 (0.744286)) delr_C = -0.0055260 +/- 0.0068920 (guessed as -0.005265 (0.007572)) ss_C = 0.0016740 +/- 0.0008460 (guessed as 0.001676 (0.000991)) enot_N = 12.4065290 +/- 1.7757010 (guessed as 12.895967 (2.018563)) delr_N = 0.0358140 +/- 0.0193390 (guessed as 0.042607 (0.029913)) ss_N = 0.0068930 +/- 0.0016280 (guessed as 0.008196 (0.002599)) enot_K = 0.0064050 +/- 9.7412920 (guessed as -4.066616 (13.931541)) delr_K = 0.9265430 +/- 0.1815320 (guessed as -0.018996 (0.154984)) ss_K = 0.0074030 +/- 0.0124260 (guessed as 0.011457 (0.010167)) enot_O = -8.4988040 +/- 13.7627610 (guessed as 0.906319 (10.059312)) delr_O = -0.3610320 +/- 0.0975640 (guessed as -0.139554 (0.069016)) ss_O = 0.0010060 +/- 0.0050660 (guessed as 0.001140 (0.004395)) Def parameters (using "FEFF0: Path 1: [C5_1]"): enot_CN = 12.5016230 delr_CN = 0.0151440 ss_CN = 0.0042840 enot_CNC = 12.5333210 delr_CNC = 0.0082540 ss_CNC = 0.0034140 enot_NCN = 12.4699250 delr_NCN = 0.0220340 ss_NCN = 0.0051540 enot_KN = 6.2064670 delr_KN = 0.4811790 ss_KN = 0.0071480 enot_KC = 6.3015610 delr_KC = 0.4605080 ss_KC = 0.0045380 enot_KNC = 8.3365500 delr_KNC = 0.3189440 ss_KNC = 0.0053230 Set parameters: enot_H = -0.920939 (0.000000) delr_H = 0.103335 (0.000000) ss_H = 0.00749823 (0.000000) Background parameters +/- uncertainties: bkg01_01 = -3437.6705554 +/- 23034.7299514 bkg01_02 = -0.0609379 +/- 1.8005458 bkg01_03 = 0.1948870 +/- 0.1595573 bkg01_04 = -0.0398830 +/- 0.0358870 bkg01_05 = -0.0025572 +/- 0.0147361 bkg01_06 = 0.0067564 +/- 0.0081250 bkg01_07 = -0.0031386 +/- 0.0052991 bkg01_08 = 0.0006703 +/- 0.0037900 bkg01_09 = -0.0000756 +/- 0.0028462 bkg01_10 = 0.0003428 +/- 0.0022025 bkg01_11 = -0.0006552 +/- 0.0017628 bkg01_12 = 0.0006924 +/- 0.0015077 bkg01_13 = -0.0004210 +/- 0.0015140 bkg01_14 = -0.0002224 +/- 0.0022632 bkg01_15 = 0.0026167 +/- 0.0075534 bkg01_16 = -0.0207863 +/- 0.0762094 bkg01_17 = 48.5761922 +/- 4197.5368888 Correlations between variables: enot_K and delr_K --> 0.8386 enot_O and delr_O --> 0.8120 enot_N and delr_N --> 0.7440 amp and ss_C --> 0.7232 enot_C and delr_C --> 0.6048 amp and enot_N --> 0.5755 enot_C and bkg01_02 --> -0.4957 amp and bkg01_05 --> 0.4817 amp and bkg01_04 --> -0.4376 enot_C and bkg01_03 --> 0.4175 enot_N and enot_O --> 0.3976 ss_C and enot_N --> 0.3902 amp and bkg01_06 --> -0.3779 amp and ss_N --> 0.3767 amp and enot_C --> -0.3652 ss_C and delr_N --> 0.3422 ss_N and bkg01_04 --> -0.3330 amp and delr_N --> 0.3325 ss_C and bkg01_15 --> -0.3311 ss_N and bkg01_05 --> 0.3172 enot_C and enot_N --> -0.3133 enot_N and bkg01_02 --> 0.2957 enot_N and delr_O --> 0.2918 delr_C and ss_N --> -0.2832 delr_N and enot_O --> 0.2804 ss_C and bkg01_16 --> 0.2690 ss_C and bkg01_05 --> 0.2663 delr_C and delr_N --> -0.2572 ss_C and bkg01_14 --> 0.2569 amp and enot_O --> 0.2560 ss_C and bkg01_04 --> -0.2528 All other correlations are below 0.25 Background parameters "bkg01_XX" belong to data set RP314a K4W(CN)8x2H2O W:L3

...

-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Scott Calvin Sent: Friday, June 19, 2009 12:23 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Zajac,

What happens if you constrain all E0's to be the same? In the fit where they come out large, what are the uncertainties in the E0's? What are their correlations with other fitted parameters? There has been some debate in this list on the past as to how useful it is to allow for different E0's for different paths. It may be that Artemis is shifting the E0's for those paths in lieu of some other correlated parameter.

--Scott Calvin Sarah Lawrence College

On Jun 19, 2009, at 5:33 AM, Zajac, Dariusz A. wrote:

...
Hi all, can anybody help me and send some link about problems with enot in Artemis? in google, tutorials I couldn't find any help. Of course are few posts about delr or ss parameters, but enot is somehow omited (or I can not find it...)

the problem is with fiting K4W(CN)8*2H2O at W:L3 edge. fit and others parameters looks ok, except enot for C and N, where both are around 12 and don't want to fit to other values... thanks darek

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

Scott Calvin

11:45 a.m.

Hi Darek, You've got a false fit. The E0's aren't the biggest problem; look at the delr for potassium! Your fit is scrambling all the paths in non- physical ways. Your initial description of the system suggests that you have a decent guess as to the structure to start with. What happens when you run a fit with very few free parameters? (Perhaps none, or perhaps just floating an overall S02, E0, and maybe a couple of sigma2's.) Does it look qualitatively right, with peaks where there should be peaks? If so, then you probably need a tighter set of constraints. If not, then the material is not what you think it is. --Scott Calvin Sarah Lawrence College On Jun 19, 2009, at 7:30 AM, Zajac, Dariusz A. wrote:

...

Hi Calvin, thanks for the email. I have tried to find something on mailing list about E0 but it seems that my "searching words" were not correct. I found only few posts but non of them explained (or followed) the problem with large enot. enot parameters are closed to eachother e.g. enot_C = 12.597(+-0.654) and enot_N=12.407(+-1.776); correlations e.g. enot_N and delr_N=0.744, enot_C and delr_C=0.605 enot_C and enot_N=-0.313 more detail you can find in the attachment or below. I have found that the value of the first background variable is large (-3437(+-23034)) when I constrain both enot's parameters I do not see huge changes in parameters, chi^2 enot, amp, delr and ssh are the same in the range of uncertainties. I agree with you that program can shift not the correct parameter, but why every time I change parameters (I shift parameters from the local minimum) their come back?

cheers darek

Independent points = 45.279296875 Number of variables = 30.000000000 Chi-square = 219223.767 Reduced Chi-square = 14347.765383235 R-factor = 0.022707172 Measurement uncertainty (k) = 0.000102780 Measurement uncertainty (R) = 0.000306293 Number of data sets = 1.000000000

Guess parameters +/- uncertainties (initial guess): amp = 0.8496050 +/- 0.0767160 (guessed as 0.849812 (0.095158)) enot_C = 12.5967170 +/- 0.6539780 (guessed as 12.601228 (0.744286)) delr_C = -0.0055260 +/- 0.0068920 (guessed as -0.005265 (0.007572)) ss_C = 0.0016740 +/- 0.0008460 (guessed as 0.001676 (0.000991)) enot_N = 12.4065290 +/- 1.7757010 (guessed as 12.895967 (2.018563)) delr_N = 0.0358140 +/- 0.0193390 (guessed as 0.042607 (0.029913)) ss_N = 0.0068930 +/- 0.0016280 (guessed as 0.008196 (0.002599)) enot_K = 0.0064050 +/- 9.7412920 (guessed as -4.066616 (13.931541)) delr_K = 0.9265430 +/- 0.1815320 (guessed as -0.018996 (0.154984)) ss_K = 0.0074030 +/- 0.0124260 (guessed as 0.011457 (0.010167)) enot_O = -8.4988040 +/- 13.7627610 (guessed as 0.906319 (10.059312)) delr_O = -0.3610320 +/- 0.0975640 (guessed as -0.139554 (0.069016)) ss_O = 0.0010060 +/- 0.0050660 (guessed as 0.001140 (0.004395))

Def parameters (using "FEFF0: Path 1: [C5_1]"): enot_CN = 12.5016230 delr_CN = 0.0151440 ss_CN = 0.0042840 enot_CNC = 12.5333210 delr_CNC = 0.0082540 ss_CNC = 0.0034140 enot_NCN = 12.4699250 delr_NCN = 0.0220340 ss_NCN = 0.0051540 enot_KN = 6.2064670 delr_KN = 0.4811790 ss_KN = 0.0071480 enot_KC = 6.3015610 delr_KC = 0.4605080 ss_KC = 0.0045380 enot_KNC = 8.3365500 delr_KNC = 0.3189440 ss_KNC = 0.0053230

Set parameters: enot_H = -0.920939 (0.000000) delr_H = 0.103335 (0.000000) ss_H = 0.00749823 (0.000000)

Background parameters +/- uncertainties: bkg01_01 = -3437.6705554 +/- 23034.7299514 bkg01_02 = -0.0609379 +/- 1.8005458 bkg01_03 = 0.1948870 +/- 0.1595573 bkg01_04 = -0.0398830 +/- 0.0358870 bkg01_05 = -0.0025572 +/- 0.0147361 bkg01_06 = 0.0067564 +/- 0.0081250 bkg01_07 = -0.0031386 +/- 0.0052991 bkg01_08 = 0.0006703 +/- 0.0037900 bkg01_09 = -0.0000756 +/- 0.0028462 bkg01_10 = 0.0003428 +/- 0.0022025 bkg01_11 = -0.0006552 +/- 0.0017628 bkg01_12 = 0.0006924 +/- 0.0015077 bkg01_13 = -0.0004210 +/- 0.0015140 bkg01_14 = -0.0002224 +/- 0.0022632 bkg01_15 = 0.0026167 +/- 0.0075534 bkg01_16 = -0.0207863 +/- 0.0762094 bkg01_17 = 48.5761922 +/- 4197.5368888

Correlations between variables: enot_K and delr_K --> 0.8386 enot_O and delr_O --> 0.8120 enot_N and delr_N --> 0.7440 amp and ss_C --> 0.7232 enot_C and delr_C --> 0.6048 amp and enot_N --> 0.5755 enot_C and bkg01_02 --> -0.4957 amp and bkg01_05 --> 0.4817 amp and bkg01_04 --> -0.4376 enot_C and bkg01_03 --> 0.4175 enot_N and enot_O --> 0.3976 ss_C and enot_N --> 0.3902 amp and bkg01_06 --> -0.3779 amp and ss_N --> 0.3767 amp and enot_C --> -0.3652 ss_C and delr_N --> 0.3422 ss_N and bkg01_04 --> -0.3330 amp and delr_N --> 0.3325 ss_C and bkg01_15 --> -0.3311 ss_N and bkg01_05 --> 0.3172 enot_C and enot_N --> -0.3133 enot_N and bkg01_02 --> 0.2957 enot_N and delr_O --> 0.2918 delr_C and ss_N --> -0.2832 delr_N and enot_O --> 0.2804 ss_C and bkg01_16 --> 0.2690 ss_C and bkg01_05 --> 0.2663 delr_C and delr_N --> -0.2572 ss_C and bkg01_14 --> 0.2569 amp and enot_O --> 0.2560 ss_C and bkg01_04 --> -0.2528 All other correlations are below 0.25

Background parameters "bkg01_XX" belong to data set RP314a K4W(CN)8x2H2O W:L3

...
-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Scott Calvin Sent: Friday, June 19, 2009 12:23 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Zajac,

What happens if you constrain all E0's to be the same? In the fit where they come out large, what are the uncertainties in the E0's? What are their correlations with other fitted parameters? There has been some debate in this list on the past as to how useful it is to allow for different E0's for different paths. It may be that Artemis is shifting the E0's for those paths in lieu of some other correlated parameter.

--Scott Calvin Sarah Lawrence College

On Jun 19, 2009, at 5:33 AM, Zajac, Dariusz A. wrote:

...
Hi all, can anybody help me and send some link about problems with enot in Artemis? in google, tutorials I couldn't find any help. Of course are few posts about delr or ss parameters, but enot is somehow omited (or I can not find it...)

the problem is with fiting K4W(CN)8*2H2O at W:L3 edge. fit and others parameters looks ok, except enot for C and N, where both are around 12 and don't want to fit to other values... thanks darek

Zajac, Dariusz A.

12:28 p.m.

Hi Scott, look also at H and O, but for me and for this fit important are only W-C and W-C-N bondings. This sample is an reference sample for other cyano-brigded networks. So you suggest to focuse on K ions? how can it help with first 2 peaks? K is at ~5A. I have analysed in larger R space only to see how the spectrum behave. contribution from K, O etc. at k highers than 5A is for me too low to analyse it resonable for such compound. I have attached in the previus post the last version of results. Anyway, enots for C and N do not change if I am enlarging R region (when I am including next paths, also for K). about material I am quite sure ;) and crystal structure is from literature in the attachment you will find bmp file of the fit: data, fit, bkg and K path. fitting ranges k(3-15) R(1.7-6) dk 2 dr 0.5, phase correction - first C cheers darek

...

-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Scott Calvin Sent: Friday, June 19, 2009 1:46 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Darek,

You've got a false fit. The E0's aren't the biggest problem; look at the delr for potassium! Your fit is scrambling all the paths in non- physical ways.

Your initial description of the system suggests that you have a decent guess as to the structure to start with. What happens when you run a fit with very few free parameters? (Perhaps none, or perhaps just floating an overall S02, E0, and maybe a couple of sigma2's.) Does it look qualitatively right, with peaks where there should be peaks? If so, then you probably need a tighter set of constraints. If not, then the material is not what you think it is.

--Scott Calvin Sarah Lawrence College

On Jun 19, 2009, at 7:30 AM, Zajac, Dariusz A. wrote:

...
Hi Calvin, thanks for the email. I have tried to find something on mailing list about E0 but it seems that my "searching words" were not correct. I found only few posts but non of them explained (or followed) the problem with large enot. enot parameters are closed to eachother e.g. enot_C = 12.597(+-0.654) and enot_N=12.407(+-1.776); correlations e.g. enot_N and delr_N=0.744, enot_C and delr_C=0.605 enot_C and enot_N=-0.313 more detail you can find in the attachment or below. I have found that the value of the first background variable is large (-3437(+-23034)) when I constrain both enot's parameters I do not see huge changes in parameters, chi^2 enot, amp, delr and ssh are the same in the range of uncertainties. I agree with you that program can shift not the correct parameter, but why every time I change parameters (I shift parameters from the local minimum) their come back?

cheers darek

Independent points = 45.279296875 Number of variables = 30.000000000 Chi-square = 219223.767 Reduced Chi-square = 14347.765383235 R-factor = 0.022707172 Measurement uncertainty (k) = 0.000102780 Measurement uncertainty (R) = 0.000306293 Number of data sets = 1.000000000

Guess parameters +/- uncertainties (initial guess): amp = 0.8496050 +/- 0.0767160 (guessed as 0.849812 (0.095158)) enot_C = 12.5967170 +/- 0.6539780 (guessed as 12.601228 (0.744286)) delr_C = -0.0055260 +/- 0.0068920 (guessed as -0.005265 (0.007572)) ss_C = 0.0016740 +/- 0.0008460 (guessed as 0.001676 (0.000991)) enot_N = 12.4065290 +/- 1.7757010 (guessed as 12.895967 (2.018563)) delr_N = 0.0358140 +/- 0.0193390 (guessed as 0.042607 (0.029913)) ss_N = 0.0068930 +/- 0.0016280 (guessed as 0.008196 (0.002599)) enot_K = 0.0064050 +/- 9.7412920 (guessed as -4.066616 (13.931541)) delr_K = 0.9265430 +/- 0.1815320 (guessed as -0.018996 (0.154984)) ss_K = 0.0074030 +/- 0.0124260 (guessed as 0.011457 (0.010167)) enot_O = -8.4988040 +/- 13.7627610 (guessed as 0.906319 (10.059312)) delr_O = -0.3610320 +/- 0.0975640 (guessed as -0.139554 (0.069016)) ss_O = 0.0010060 +/- 0.0050660 (guessed as 0.001140 (0.004395))

Def parameters (using "FEFF0: Path 1: [C5_1]"): enot_CN = 12.5016230 delr_CN = 0.0151440 ss_CN = 0.0042840 enot_CNC = 12.5333210 delr_CNC = 0.0082540 ss_CNC = 0.0034140 enot_NCN = 12.4699250 delr_NCN = 0.0220340 ss_NCN = 0.0051540 enot_KN = 6.2064670 delr_KN = 0.4811790 ss_KN = 0.0071480 enot_KC = 6.3015610 delr_KC = 0.4605080 ss_KC = 0.0045380 enot_KNC = 8.3365500 delr_KNC = 0.3189440 ss_KNC = 0.0053230

Set parameters: enot_H = -0.920939 (0.000000) delr_H = 0.103335 (0.000000) ss_H = 0.00749823 (0.000000)

Background parameters +/- uncertainties: bkg01_01 = -3437.6705554 +/- 23034.7299514 bkg01_02 = -0.0609379 +/- 1.8005458 bkg01_03 = 0.1948870 +/- 0.1595573 bkg01_04 = -0.0398830 +/- 0.0358870 bkg01_05 = -0.0025572 +/- 0.0147361 bkg01_06 = 0.0067564 +/- 0.0081250 bkg01_07 = -0.0031386 +/- 0.0052991 bkg01_08 = 0.0006703 +/- 0.0037900 bkg01_09 = -0.0000756 +/- 0.0028462 bkg01_10 = 0.0003428 +/- 0.0022025 bkg01_11 = -0.0006552 +/- 0.0017628 bkg01_12 = 0.0006924 +/- 0.0015077 bkg01_13 = -0.0004210 +/- 0.0015140 bkg01_14 = -0.0002224 +/- 0.0022632 bkg01_15 = 0.0026167 +/- 0.0075534 bkg01_16 = -0.0207863 +/- 0.0762094 bkg01_17 = 48.5761922 +/- 4197.5368888

Correlations between variables: enot_K and delr_K --> 0.8386 enot_O and delr_O --> 0.8120 enot_N and delr_N --> 0.7440 amp and ss_C --> 0.7232 enot_C and delr_C --> 0.6048 amp and enot_N --> 0.5755 enot_C and bkg01_02 --> -0.4957 amp and bkg01_05 --> 0.4817 amp and bkg01_04 --> -0.4376 enot_C and bkg01_03 --> 0.4175 enot_N and enot_O --> 0.3976 ss_C and enot_N --> 0.3902 amp and bkg01_06 --> -0.3779 amp and ss_N --> 0.3767 amp and enot_C --> -0.3652 ss_C and delr_N --> 0.3422 ss_N and bkg01_04 --> -0.3330 amp and delr_N --> 0.3325 ss_C and bkg01_15 --> -0.3311 ss_N and bkg01_05 --> 0.3172 enot_C and enot_N --> -0.3133 enot_N and bkg01_02 --> 0.2957 enot_N and delr_O --> 0.2918 delr_C and ss_N --> -0.2832 delr_N and enot_O --> 0.2804 ss_C and bkg01_16 --> 0.2690 ss_C and bkg01_05 --> 0.2663 delr_C and delr_N --> -0.2572 ss_C and bkg01_14 --> 0.2569 amp and enot_O --> 0.2560 ss_C and bkg01_04 --> -0.2528 All other correlations are below 0.25

...
-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Scott Calvin Sent: Friday, June 19, 2009 12:23 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Zajac,

What happens if you constrain all E0's to be the same? In the fit where they come out large, what are the uncertainties in the E0's? What are their correlations with other fitted parameters? There has been some debate in this list on the past as to how useful it is to allow for different E0's for different paths. It may be

Background parameters "bkg01_XX" belong to data set RP314a K4W(CN)8x2H2O W:L3 that Artemis

...
is shifting the E0's for those paths in lieu of some other correlated parameter.

--Scott Calvin Sarah Lawrence College

On Jun 19, 2009, at 5:33 AM, Zajac, Dariusz A. wrote:

...
Hi all, can anybody help me and send some link about problems with enot in Artemis? in google, tutorials I couldn't find any help. Of course are few posts about delr or ss parameters, but enot is somehow omited (or I can not find it...)

the problem is with fiting K4W(CN)8*2H2O at W:L3 edge. fit and others parameters looks ok, except enot for C and N, where both are around 12 and don't want to fit to other values... thanks darek

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

Scott Calvin

12:48 p.m.

Hi Darek, OK, so if the K, H, and O don't affect the fit much for the C and N, and the K, H, and O are returning nonsensical values, then a logical possibility is that the E0's for C and N are correct. If you add 12 eV to the E0 you chose in Athena, where in the spectrum does it fall? Is it still before the white line? If so, it seems to me you don't have a problem. If not, then we have to ponder further. --Scott Calvin Sarah Lawrence College On Jun 19, 2009, at 8:28 AM, Zajac, Dariusz A. wrote:

...

Hi Scott, look also at H and O, but for me and for this fit important are only W-C and W-C-N bondings. This sample is an reference sample for other cyano-brigded networks. So you suggest to focuse on K ions? how can it help with first 2 peaks? K is at ~5A. I have analysed in larger R space only to see how the spectrum behave. contribution from K, O etc. at k highers than 5A is for me too low to analyse it resonable for such compound. I have attached in the previus post the last version of results. Anyway, enots for C and N do not change if I am enlarging R region (when I am including next paths, also for K). about material I am quite sure ;) and crystal structure is from literature

in the attachment you will find bmp file of the fit: data, fit, bkg and K path. fitting ranges k(3-15) R(1.7-6) dk 2 dr 0.5, phase correction - first C

cheers darek

Zajac, Dariusz A.

2:44 p.m.

Hi Scott, I am afraid that E0 jumps over the edge - see bmp's in the attachment (files with enot_12 means E0=12...). Hovewer 12 eV is still less than k=3 (the starting k value). Can it influence? I did also once more fit with R from 1.7 to 4A. Fits of first 2 peaks are identical - you can see in the attachment too... I hope you and anyone from the mailing list don't mind that I am attaching so many files... cheers darek

...

-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Scott Calvin Sent: Friday, June 19, 2009 2:49 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Darek,

OK, so if the K, H, and O don't affect the fit much for the C and N, and the K, H, and O are returning nonsensical values, then a logical possibility is that the E0's for C and N are correct. If you add 12 eV to the E0 you chose in Athena, where in the spectrum does it fall? Is it still before the white line? If so, it seems to me you don't have a problem. If not, then we have to ponder further.

--Scott Calvin Sarah Lawrence College

On Jun 19, 2009, at 8:28 AM, Zajac, Dariusz A. wrote:

...
Hi Scott, look also at H and O, but for me and for this fit important are only W-C and W-C-N bondings. This sample is an reference sample for other cyano-brigded networks. So you suggest to focuse on K ions? how can it help with first 2 peaks? K is at ~5A. I have analysed in larger R space only to see how the spectrum behave. contribution from K, O etc. at k highers than 5A is for me too low to analyse it resonable for such compound. I have attached in the previus post the last version of results. Anyway, enots for C and N do not change if I am enlarging R region (when I am including next paths, also for K). about material I am quite sure ;) and crystal structure is from literature

in the attachment you will find bmp file of the fit: data, fit, bkg and K path. fitting ranges k(3-15) R(1.7-6) dk 2 dr 0.5, phase correction - first C

cheers darek

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

Kropf, Arthur Jeremy

7:41 p.m.

With the very strong white lines at the L3 edges of oxidized Pt, W, Ir, etc., there is no reason to assume that Eo is on the lower energy side of the peak. Jeremy Kropf

...

-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Zajac, Dariusz A. Sent: Friday, June 19, 2009 9:45 AM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Scott, I am afraid that E0 jumps over the edge - see bmp's in the attachment (files with enot_12 means E0=12...). Hovewer 12 eV is still less than k=3 (the starting k value). Can it influence? I did also once more fit with R from 1.7 to 4A. Fits of first 2 peaks are identical - you can see in the attachment too... I hope you and anyone from the mailing list don't mind that I am attaching so many files...

cheers darek

...
-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Scott Calvin Sent: Friday, June 19, 2009 2:49 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Darek,

OK, so if the K, H, and O don't affect the fit much for the C and N, and the K, H, and O are returning nonsensical values, then a logical possibility is that the E0's for C and N are correct. If you add 12 eV to the E0 you chose in Athena, where in the spectrum does it fall? Is it still before the white line? If so, it seems to me you don't have a problem. If not, then we have to ponder further.

--Scott Calvin Sarah Lawrence College

On Jun 19, 2009, at 8:28 AM, Zajac, Dariusz A. wrote:

...
Hi Scott, look also at H and O, but for me and for this fit important are only W-C and W-C-N bondings. This sample is an reference sample for other cyano-brigded networks. So you suggest to focuse on K ions? how can it help with first 2 peaks? K is at ~5A. I have analysed in larger R space only to see how the spectrum behave. contribution from K, O etc. at k highers than 5A is for me too low to analyse it resonable for such compound. I have attached in the previus post the last version of results. Anyway, enots for C and N do not change if I am enlarging R region (when I am including next paths, also for K). about material I am quite sure ;) and crystal structure is from literature

in the attachment you will find bmp file of the fit: data, fit, bkg and K path. fitting ranges k(3-15) R(1.7-6) dk 2 dr 0.5, phase correction - first C

cheers darek

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

Frenkel, Anatoly

7:44 p.m.

Just a comment, to add some sanity in this discussion: FEFF6 is overestimating delta E0 for Pt and a few other metals. I forgot the reason but it could be the cause of a problem. I think FEFF8 is doing a better job. Fortunately - and it was checked - no other problems occur, just E0 values change, when one usees FEFF8 instead of FEFF6 in most cases. Anatoly ________________________________ From: ifeffit-bounces@millenia.cars.aps.anl.gov on behalf of Kropf, Arthur Jeremy Sent: Fri 6/19/2009 3:41 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters With the very strong white lines at the L3 edges of oxidized Pt, W, Ir, etc., there is no reason to assume that Eo is on the lower energy side of the peak. Jeremy Kropf

...

-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Zajac, Dariusz A. Sent: Friday, June 19, 2009 9:45 AM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Scott, I am afraid that E0 jumps over the edge - see bmp's in the attachment (files with enot_12 means E0=12...). Hovewer 12 eV is still less than k=3 (the starting k value). Can it influence? I did also once more fit with R from 1.7 to 4A. Fits of first 2 peaks are identical - you can see in the attachment too... I hope you and anyone from the mailing list don't mind that I am attaching so many files...

cheers darek

...
-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Scott Calvin Sent: Friday, June 19, 2009 2:49 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Darek,

OK, so if the K, H, and O don't affect the fit much for the C and N, and the K, H, and O are returning nonsensical values, then a logical possibility is that the E0's for C and N are correct. If you add 12 eV to the E0 you chose in Athena, where in the spectrum does it fall? Is it still before the white line? If so, it seems to me you don't have a problem. If not, then we have to ponder further.

--Scott Calvin Sarah Lawrence College

On Jun 19, 2009, at 8:28 AM, Zajac, Dariusz A. wrote:

...
Hi Scott, look also at H and O, but for me and for this fit important are only W-C and W-C-N bondings. This sample is an reference sample for other cyano-brigded networks. So you suggest to focuse on K ions? how can it help with first 2 peaks? K is at ~5A. I have analysed in larger R space only to see how the spectrum behave. contribution from K, O etc. at k highers than 5A is for me too low to analyse it resonable for such compound. I have attached in the previus post the last version of results. Anyway, enots for C and N do not change if I am enlarging R region (when I am including next paths, also for K). about material I am quite sure ;) and crystal structure is from literature

in the attachment you will find bmp file of the fit: data, fit, bkg and K path. fitting ranges k(3-15) R(1.7-6) dk 2 dr 0.5, phase correction - first C

cheers darek

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

Zajac, Dariusz A.

20 Jun 20 Jun

8:37 a.m.

New subject: ODP: problem with E0 (enot) parameters

Dear Jeremy, thanks for your reply. This fits to my results and to my "feeling", but is any physical meaning behind it? cheers darek -----Wiadomość oryginalna----- Od: ifeffit-bounces@millenia.cars.aps.anl.gov w imieniu Kropf, Arthur Jeremy Wysłano: Pt 2009-06-19 21:41 Do: XAFS Analysis using Ifeffit Temat: Re: [Ifeffit] problem with E0 (enot) parameters With the very strong white lines at the L3 edges of oxidized Pt, W, Ir, etc., there is no reason to assume that Eo is on the lower energy side of the peak. Jeremy Kropf

...

-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Zajac, Dariusz A. Sent: Friday, June 19, 2009 9:45 AM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Scott, I am afraid that E0 jumps over the edge - see bmp's in the attachment (files with enot_12 means E0=12...). Hovewer 12 eV is still less than k=3 (the starting k value). Can it influence? I did also once more fit with R from 1.7 to 4A. Fits of first 2 peaks are identical - you can see in the attachment too... I hope you and anyone from the mailing list don't mind that I am attaching so many files...

cheers darek

...
-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Scott Calvin Sent: Friday, June 19, 2009 2:49 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Darek,

OK, so if the K, H, and O don't affect the fit much for the C and N, and the K, H, and O are returning nonsensical values, then a logical possibility is that the E0's for C and N are correct. If you add 12 eV to the E0 you chose in Athena, where in the spectrum does it fall? Is it still before the white line? If so, it seems to me you don't have a problem. If not, then we have to ponder further.

--Scott Calvin Sarah Lawrence College

On Jun 19, 2009, at 8:28 AM, Zajac, Dariusz A. wrote:

...
Hi Scott, look also at H and O, but for me and for this fit important are only W-C and W-C-N bondings. This sample is an reference sample for other cyano-brigded networks. So you suggest to focuse on K ions? how can it help with first 2 peaks? K is at ~5A. I have analysed in larger R space only to see how the spectrum behave. contribution from K, O etc. at k highers than 5A is for me too low to analyse it resonable for such compound. I have attached in the previus post the last version of results. Anyway, enots for C and N do not change if I am enlarging R region (when I am including next paths, also for K). about material I am quite sure ;) and crystal structure is from literature

in the attachment you will find bmp file of the fit: data, fit, bkg and K path. fitting ranges k(3-15) R(1.7-6) dk 2 dr 0.5, phase correction - first C

cheers darek

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

Stefan Mangold

10:44 a.m.

Please do not attach 10 Mb of data on your Mails. Just send an Link to an Web-space with your e-mail. People can then download the stuff if needed. Best regards Stefan Am 19.06.2009 um 16:44 schrieb Zajac, Dariusz A.:

...

Hi Scott, I am afraid that E0 jumps over the edge - see bmp's in the attachment (files with enot_12 means E0=12...). Hovewer 12 eV is still less than k=3 (the starting k value). Can it influence? I did also once more fit with R from 1.7 to 4A. Fits of first 2 peaks are identical - you can see in the attachment too... I hope you and anyone from the mailing list don't mind that I am attaching so many files...

cheers darek

...
-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Scott Calvin Sent: Friday, June 19, 2009 2:49 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Darek,

OK, so if the K, H, and O don't affect the fit much for the C and N, and the K, H, and O are returning nonsensical values, then a logical possibility is that the E0's for C and N are correct. If you add 12 eV to the E0 you chose in Athena, where in the spectrum does it fall? Is it still before the white line? If so, it seems to me you don't have a problem. If not, then we have to ponder further.

--Scott Calvin Sarah Lawrence College

On Jun 19, 2009, at 8:28 AM, Zajac, Dariusz A. wrote:

...
Hi Scott, look also at H and O, but for me and for this fit important are only W-C and W-C-N bondings. This sample is an reference sample for other cyano-brigded networks. So you suggest to focuse on K ions? how can it help with first 2 peaks? K is at ~5A. I have analysed in larger R space only to see how the spectrum behave. contribution from K, O etc. at k highers than 5A is for me too low to analyse it resonable for such compound. I have attached in the previus post the last version of results. Anyway, enots for C and N do not change if I am enlarging R region (when I am including next paths, also for K). about material I am quite sure ;) and crystal structure is from literature

in the attachment you will find bmp file of the fit: data, fit, bkg and K path. fitting ranges k(3-15) R(1.7-6) dk 2 dr 0.5, phase correction - first C

cheers darek

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

< K4W (CN )8_enot_12 .bmp

...
< K4W (CN )8_enot_0.bmp><mime- attachment.txt>

-- Dr. Stefan Mangold Institut für Synchrotronstrahlung Forschungszentrum Karlsruhe Tel.: +49-7247-826073

Zajac, Dariusz A.

2:37 p.m.

New subject: ODP: problem with E0 (enot) parameters

I appologize, first and last time... cheers darek -----Wiadomość oryginalna----- Od: ifeffit-bounces@millenia.cars.aps.anl.gov w imieniu Stefan Mangold Wysłano: So 2009-06-20 12:44 Do: XAFS Analysis using Ifeffit Temat: Re: [Ifeffit] problem with E0 (enot) parameters Please do not attach 10 Mb of data on your Mails. Just send an Link to an Web-space with your e-mail. People can then download the stuff if needed. Best regards Stefan Am 19.06.2009 um 16:44 schrieb Zajac, Dariusz A.:

...

Hi Scott, I am afraid that E0 jumps over the edge - see bmp's in the attachment (files with enot_12 means E0=12...). Hovewer 12 eV is still less than k=3 (the starting k value). Can it influence? I did also once more fit with R from 1.7 to 4A. Fits of first 2 peaks are identical - you can see in the attachment too... I hope you and anyone from the mailing list don't mind that I am attaching so many files...

cheers darek

...
-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Scott Calvin Sent: Friday, June 19, 2009 2:49 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Darek,

OK, so if the K, H, and O don't affect the fit much for the C and N, and the K, H, and O are returning nonsensical values, then a logical possibility is that the E0's for C and N are correct. If you add 12 eV to the E0 you chose in Athena, where in the spectrum does it fall? Is it still before the white line? If so, it seems to me you don't have a problem. If not, then we have to ponder further.

--Scott Calvin Sarah Lawrence College

On Jun 19, 2009, at 8:28 AM, Zajac, Dariusz A. wrote:

...
Hi Scott, look also at H and O, but for me and for this fit important are only W-C and W-C-N bondings. This sample is an reference sample for other cyano-brigded networks. So you suggest to focuse on K ions? how can it help with first 2 peaks? K is at ~5A. I have analysed in larger R space only to see how the spectrum behave. contribution from K, O etc. at k highers than 5A is for me too low to analyse it resonable for such compound. I have attached in the previus post the last version of results. Anyway, enots for C and N do not change if I am enlarging R region (when I am including next paths, also for K). about material I am quite sure ;) and crystal structure is from literature

in the attachment you will find bmp file of the fit: data, fit, bkg and K path. fitting ranges k(3-15) R(1.7-6) dk 2 dr 0.5, phase correction - first C

cheers darek

_______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

< K4W (CN )8_enot_12 .bmp

...
< K4W (CN )8_enot_0.bmp><mime- attachment.txt>

-- Dr. Stefan Mangold Institut für Synchrotronstrahlung Forschungszentrum Karlsruhe Tel.: +49-7247-826073

Scott Calvin

8:39 p.m.

New subject: ODP: problem with E0 (enot) parameters

My email system didn't even let the message through, so I lost the thread for a bit. On the other hand, I for one DO want to encourage people to attach stuff that's less than 2 Mb when appropriate. It's very convenient to have, say, an Artemis project file to look at in some cases, and I often look at/write responses to these emails when I'm not connected to the web and thus can't follow a link. Is that an OK rule of thumb with the rest of you? Under 2 Mb => OK to attach; over 2 Mb use a link? Or would people prefer a lower threshold? --Scott Calvin Sarah Lawrence College On Jun 20, 2009, at 10:37 AM, Zajac, Dariusz A. wrote:

...

I appologize, first and last time... cheers darek

-----Wiadomość oryginalna----- Od: ifeffit-bounces@millenia.cars.aps.anl.gov w imieniu Stefan Mangold Wysłano: So 2009-06-20 12:44 Do: XAFS Analysis using Ifeffit Temat: Re: [Ifeffit] problem with E0 (enot) parameters

Please do not attach 10 Mb of data on your Mails. Just send an Link to an Web-space with your e-mail. People can then download the stuff if needed.

Best regards

Stefan

Matt Newville

3:40 p.m.

Hi Dariusz, Just to follow up on Stefan's request to not post large attachments to email: The ifeffit web page is a wiki, and would be an ideal place for posting the data (feff inputs, project files, images of plots) for such questions. You can read up on the wiki page for how to do create pages and post attachments. I'd encourage anyone with similar impulses to post large files to use the wiki for such discussions. To follow up on the rest of your questions and this thread: I agree with Jeremy's advice / observation that having an E0 shift push E0 "over the white line" is not so unusual when using Feff6, especially for L3 edges. I'm not sure there's a good reason for it besides "Feff6 makes approximations". I'd also add a few other points: 1. In your original post, you had a huge number (30!) of variables. I'd recommend that you start much more simply than that. In particular, I'd suggest starting without refining the background. 2. As you know, It's hard for EXAFS to distinguish between C, N, and O backscatters, and so "flipping atoms" around to positions that are "obviously incorrect but consistent with the EXAFS data" is something you'll need to look out for, especially with so many variables (see point 1). 3. My understanding is that W L3 is particularly hard. If you haven't already done so, I'd suggest checking the literature on this and doing as many sanity checks as possible. --Matt

Zajac, Dariusz A.

8:38 p.m.

New subject: ODP: problem with E0 (enot) parameters

Dear Scott, dear Arthur, dear Anatoly, dear Josh, dear Matt and dears All, thank a lot for you involement in my problem. I would like once more to appologize for that stupid idea to post message with large attachment, once I know I shouldn't do it, second I should check how large the files are... I posted the message just before I left home and when I checked it home was too late - I couldn't cancel my post... thanks once more. Dear Matt, answering to your post: ad 1 - I have fitted up to 6A just to see the fit, the resonable fot can be only for first 2 peaks for C and N. Adding next parameters do not change the E0. the free parameters I had are only C and N, rest is combination of these 2 + extra for H, O, K at higher R. I have to check once more how the fit is without background. ad 2 - I have no problem with distinguishing C and N - the sample is quite well ordered - cyano bridges. Only the multipath scaterring between C and N gives the contribution to first 2 peaks, but it is not possible to have good fit without them, thus I think the fit I have obtained is resonable even large E0. I do not observe flipping of atoms. ad 3 - yap, I havent worked with W, thus I asked you. once more thanks for teh help and good advices cheers darek -----Wiadomość oryginalna----- Od: ifeffit-bounces@millenia.cars.aps.anl.gov w imieniu Matt Newville Wysłano: So 2009-06-20 17:40 Do: XAFS Analysis using Ifeffit Temat: Re: [Ifeffit] problem with E0 (enot) parameters Hi Dariusz, Just to follow up on Stefan's request to not post large attachments to email: The ifeffit web page is a wiki, and would be an ideal place for posting the data (feff inputs, project files, images of plots) for such questions. You can read up on the wiki page for how to do create pages and post attachments. I'd encourage anyone with similar impulses to post large files to use the wiki for such discussions. To follow up on the rest of your questions and this thread: I agree with Jeremy's advice / observation that having an E0 shift push E0 "over the white line" is not so unusual when using Feff6, especially for L3 edges. I'm not sure there's a good reason for it besides "Feff6 makes approximations". I'd also add a few other points: 1. In your original post, you had a huge number (30!) of variables. I'd recommend that you start much more simply than that. In particular, I'd suggest starting without refining the background. 2. As you know, It's hard for EXAFS to distinguish between C, N, and O backscatters, and so "flipping atoms" around to positions that are "obviously incorrect but consistent with the EXAFS data" is something you'll need to look out for, especially with so many variables (see point 1). 3. My understanding is that W L3 is particularly hard. If you haven't already done so, I'd suggest checking the literature on this and doing as many sanity checks as possible. --Matt _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

Zajac, Dariusz A.

22 Jun 22 Jun

2:44 p.m.

Hi all, I had followed your advices and I can shortly summarised what I've got. I fitted with and without background with feff 6 and feff 8.4. For feff 8.4 I did also with SCF=4.0 I fitted only first two peaks (R(1.7-4A) k(3-15A^(-1))) for feff 6 and feff 8.4 I had the same values of E0 for N and C, non using self-consistent potential, using it enot became smaller. All other parameters are playing around, within th error bars. fits with bkg and without it have very simnillar results, see below. more you can find on pictures: http://yfrog.com/29k4wcn8compbkgpx http://img81.imageshack.us/i/k4wcn8feff84.png/ _comp_bkg : comparison of different feff fits with bkg _feff6 : with and without bkg for feff6 _feff8.4 : as above for ver 8.4 cheers darek statistical parameters # Fitting Na2WO4_W_L3.chi # report on "Statistical parameters" # ----------------------------------------------------------------- # fit FoM R-factor Reduced_chi-square Chi-square nvar nidp 'K4W(CN)8 R(1.7-6)' 1 0.0227 14347.765 219223.767 30 45 'K4W(CN)8 R(1.7-4) no bkg' 3 0.0257 18704.721 192125.245 7 17 'K4W(CN)8 R(1.7-4) with bkg' 4 0.0211 32207.729 196737.642 24 30 'K4W(CN)8 R(1.7-4) no bkg feff 8.4' 5 0.0284 18350.504 188486.912 7 17 'K4W(CN)8 R(1.7-4) with bkg feff 8.4' 6 0.0228 29638.929 181046.387 24 30 'K4W(CN)8 R(1.7-4) bkg SCF' 10 0.0251 33785.217 206373.569 24 30 Enot_C # Fitting Na2WO4_W_L3.chi # report on "enot_C" # ----------------------------------------------------------------- # fit FoM enot_C +/- initial 'K4W(CN)8 R(1.7-6)' 1 12.5967170 0.6539780 12.601228 (0.744286) 'K4W(CN)8 R(1.7-4) no bkg' 3 13.6410110 1.0472200 13.641011 (1.047220) 'K4W(CN)8 R(1.7-4) with bkg' 4 13.5499020 1.7066630 13.549902 (1.706663) 'K4W(CN)8 R(1.7-4) no bkg feff 8.4' 5 16.9324090 0.9260820 16.932409 (0.926082) 'K4W(CN)8 R(1.7-4) with bkg feff 8.4' 6 16.5096270 1.5718970 16.509228 (1.571714) 'K4W(CN)8 R(1.7-4) bkg SCF' 10 4.1640860 1.5582580 4.164119 (1.558271) Enot_N # Fitting Na2WO4_W_L3.chi # report on "enot_N" # ----------------------------------------------------------------- # fit FoM enot_N +/- initial 'K4W(CN)8 R(1.7-6)' 1 12.4065290 1.7757010 12.895967 (2.018563) 'K4W(CN)8 R(1.7-4) no bkg' 3 10.5289150 2.3544970 10.528916 (2.354497) 'K4W(CN)8 R(1.7-4) with bkg' 4 10.4310180 3.5828820 10.431018 (3.582882) 'K4W(CN)8 R(1.7-4) no bkg feff 8.4' 5 23.3734610 1.2695440 23.373461 (1.269544) 'K4W(CN)8 R(1.7-4) with bkg feff 8.4' 6 24.5886140 5.7410720 24.590866 (5.737253) 'K4W(CN)8 R(1.7-4) bkg SCF' 10 2.2653510 4.7905060 2.265237 (4.790501)

...

-----Original Message----- From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of Matt Newville Sent: Saturday, June 20, 2009 5:41 PM To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] problem with E0 (enot) parameters

Hi Dariusz,

Just to follow up on Stefan's request to not post large attachments to email:

The ifeffit web page is a wiki, and would be an ideal place for posting the data (feff inputs, project files, images of plots) for such questions. You can read up on the wiki page for how to do create pages and post attachments. I'd encourage anyone with similar impulses to post large files to use the wiki for such discussions.

To follow up on the rest of your questions and this thread:

I agree with Jeremy's advice / observation that having an E0 shift push E0 "over the white line" is not so unusual when using Feff6, especially for L3 edges. I'm not sure there's a good reason for it besides "Feff6 makes approximations".

I'd also add a few other points: 1. In your original post, you had a huge number (30!) of variables. I'd recommend that you start much more simply than that. In particular, I'd suggest starting without refining the background. 2. As you know, It's hard for EXAFS to distinguish between C, N, and O backscatters, and so "flipping atoms" around to positions that are "obviously incorrect but consistent with the EXAFS data" is something you'll need to look out for, especially with so many variables (see point 1). 3. My understanding is that W L3 is particularly hard. If you haven't already done so, I'd suggest checking the literature on this and doing as many sanity checks as possible.

--Matt _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit

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Frenkel, Anatoly
Kropf, Arthur Jeremy
Matt Newville
Scott Calvin
Stefan Mangold
Zajac, Dariusz A.