[Ifeffit] Fitting Commercial Molybdenum Disulfide
Kelly, Shelly D.
SKelly at anl.gov
Thu Nov 4 13:58:07 CST 2004
Hi Dan,
Sigma2 can not be negative. It is the mean square displacement of the
half path length. You can force it to be positive by using abs(ss) on
the definition page for each path in the fit.
Shelly
> -----Original Message-----
> From: dmc at pdx.edu [mailto:dmc at pdx.edu]
> Sent: Thursday, November 04, 2004 10:19 AM
> To: XAFS Analysis using Ifeffit
> Subject: Re: [Ifeffit] Fitting Commercial Molybdenum Disulfide
>
> Hi List,
>
> Here's my most recent data. I was able to look at the individual
> paths
> and changed my R-range to 2-4.5 angstroms on the first set of data, I
set
> the
> second set of data to the same range, although 4 works better as a
maximum
> for
> that set. The k-range on the second range had to be truncated though.
>
> Six paths are used for each fit, same parameters, except for amp (0.7
for
> one
> ~0.8 for the other). The seperate data sets still have a few
parameters
> that
> are outside of the error bars of the other (ss2,ss3,ss4,alpha,
> alpha2,alpha5).
> What can I do to get these beamlines to agree?
>
> delr_# define alpha# * reff
> all other parameters guessed.
> ss for each path, only one e0 for all
>
> Thanks for the help, Dan
>
>
> First Data set -- Full k-range works best, Full range used for fit.
> Project title : Fitting merge 10_15_04.chi
>
> Guess parameters +/- uncertainties (initial guess):
> e0 = 0.8686930 +/- 1.1038290 (guessed as 0.868694
> (1.103841))
> ss = 0.0041150 +/- 0.0004990 (guessed as 0.004115
> (0.000499))
> ss2 = 0.0044360 +/- 0.0004450 (guessed as 0.004436
> (0.000445))
> ss3 = 0.0243560 +/- 0.0201400 (guessed as 0.024368
> (0.020159))
> ss4 = -0.0065470 +/- 0.0047820 (guessed as -0.006545
> (0.004786))
> ss5 = -0.0016100 +/- 0.0050490 (guessed as -0.001611
> (0.005047))
> ss6 = 0.0059980 +/- 0.0139390 (guessed as 0.005996
> (0.013935))
> alpha = -0.0011360 +/- 0.0029380 (guessed as -0.001136
> (0.002938))
> alpha2 = 0.0071480 +/- 0.0019780 (guessed as 0.007148
> (0.001978))
> alpha3 = -0.0060900 +/- 0.0273580 (guessed as -0.006078
> (0.027378))
> alpha4 = -0.0198570 +/- 0.0154200 (guessed as -0.019851
> (0.015430))
> alpha5 = 0.1399050 +/- 0.0148530 (guessed as 0.139906
> (0.014848))
> alpha6 = 0.0199630 +/- 0.0268690 (guessed as 0.019961
> (0.026862))
>
> Def parameters:
> delr_1 = -0.0051820
> delr_2 = 0.0326180
> delr_3 = -0.0277930
> delr_4 = -0.0906110
> delr_5 = 0.6384270
> delr_6 = 0.0910950
>
> Set parameters:
> amp1 = .7
>
>
> Correlations between variables:
> e0 and alpha --> 0.8170
> e0 and alpha2 --> 0.6726
> ss and ss2 --> 0.6591
> alpha and alpha2 --> 0.5516
> alpha5 and alpha6 --> -0.4856
> e0 and alpha3 --> 0.4083
> alpha3 and alpha4 --> 0.3588
> ss5 and ss6 --> -0.3581
> alpha and alpha3 --> 0.3100
> alpha2 and alpha3 --> 0.3045
> ss2 and alpha6 --> 0.2745
> e0 and ss3 --> 0.2649
> ss and ss3 --> 0.2627
> ss2 and ss3 --> 0.2626
> ss6 and alpha5 --> -0.2510
> All other correlations are below 0.25
>
>
>
>
>
>
>
>
>
>
>
> Second Data Set -- Trucated k-range (2-13.5)
> Project title : Fitting merge 10_15_04.chi
>
> Independent points = 25.270507813
> Number of variables = 14.000000000
> Chi-square = 1202.598221935
> Reduced Chi-square = 106.703108852
> R-factor = 0.057229121
> Measurement uncertainty (k) = 0.000827712
> Measurement uncertainty (R) = 0.022111003
> Number of data sets = 1.000000000
>
>
> Guess parameters +/- uncertainties (initial guess):
> amp = 0.7976070 +/- 0.1361170 (guessed as 0.776348
(0.139898))
> ss = 0.0037770 +/- 0.0015530 (guessed as 0.003589
> (0.001617))
> e0 = 0.5608430 +/- 1.8018380 (guessed as 0.642687
> (1.861307))
> alpha = -0.0061290 +/- 0.0049080 (guessed as -0.005966
> (0.005078))
> ss2 = 0.0029050 +/- 0.0009970 (guessed as 0.002686
> (0.001078))
> ss3 = 0.0075410 +/- 0.0094220 (guessed as 0.005992
> (0.008858))
> ss4 = -0.0110250 +/- 0.0035850 (guessed as -0.011776
> (0.004653))
> ss5 = -0.0042000 +/- 0.0078070 (guessed as -0.007610
> (0.005250))
> alpha2 = 0.0038110 +/- 0.0030450 (guessed as 0.003762
> (0.003187))
> alpha3 = -0.0037820 +/- 0.0145580 (guessed as 0.001200
> (0.015976))
> alpha4 = -0.0212550 +/- 0.0107080 (guessed as -0.011852
> (0.014417))
> alpha5 = 0.1151980 +/- 0.0236640 (guessed as 0.113430
> (0.014973))
> ss6 = 0.0028560 +/- 0.0166050 (guessed as -0.007250
> (0.003624))
> alpha6 = 0.0193530 +/- 0.0299640 (guessed as 0.001791
> (0.008195))
>
> Def parameters:
> delr_1 = -0.0279670
> delr_2 = 0.0173920
> delr_3 = -0.0172570
> delr_4 = -0.0969910
> delr_5 = 0.5256830
> delr_6 = 0.0883130
>
>
> Correlations between variables:
> amp and ss --> 0.8382
> e0 and alpha --> 0.8048
> amp and ss2 --> 0.7964
> e0 and alpha2 --> 0.7533
> ss3 and alpha5 --> 0.7397
> ss5 and alpha4 --> -0.6999
> ss and ss2 --> 0.6591
> alpha and alpha2 --> 0.6159
> alpha5 and ss6 --> 0.6116
> ss5 and alpha3 --> -0.5790
> ss5 and alpha6 --> -0.5023
> ss3 and ss6 --> 0.4804
> alpha4 and alpha5 --> -0.4375
> e0 and alpha3 --> 0.4083
> ss4 and ss5 --> -0.4047
> ss3 and alpha4 --> -0.3972
> alpha5 and alpha6 --> 0.3827
> alpha3 and alpha6 --> 0.3498
> ss3 and ss5 --> -0.3278
> amp and ss3 --> 0.3209
> ss4 and ss6 --> 0.3181
> alpha and alpha3 --> 0.3100
> alpha2 and alpha3 --> 0.3045
> ss4 and alpha3 --> 0.2948
> amp and ss5 --> 0.2820
> ss2 and alpha6 --> 0.2745
> ss and ss3 --> 0.2627
> ss2 and ss3 --> 0.2626
> amp and alpha6 --> 0.2589
> alpha2 and alpha5 --> 0.2581
> All other correlations are below 0.25
>
>
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