[Ifeffit] problem with E0 (enot) parameters
Zajac, Dariusz A.
dariusz.zajac at desy.de
Fri Jun 19 06:30:31 CDT 2009
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 at millenia.cars.aps.anl.gov
>[mailto:ifeffit-bounces at 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 at millenia.cars.aps.anl.gov
>http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: K4WCN8-exafs fit.log
Type: application/octet-stream
Size: 67544 bytes
Desc: K4WCN8-exafs fit.log
URL: <http://millenia.cars.aps.anl.gov/pipermail/ifeffit/attachments/20090619/acd571d8/attachment.obj>
More information about the Ifeffit
mailing list