[Ifeffit] Linear Combination Fit
Christoph Sahle
christoph.sahle at tu-dortmund.de
Thu May 12 06:28:05 CDT 2011
Dear Dr. Kelly,
this was not my question in the first place, but I am still super
interested in your book/book chapter on LC fitting. Would you send me a
pdf-copy as well?
Thanks so much, I am learning a lot through the ifeffit mailing list!
Cheers
Christoph
> Hi Saugata
>
> With appropriate standards, the sum of scaling factors equals 1, so that
> the
> sum of the fractions of all
> chemical species of an element equals the relative amount of the element
> in
> the sample.
> Physically, the spectra from a standard might contain more atomic scale
> order than the representation
> of that component. Structural disorder could be represented in the XANES
> spectra by a broadening of the spectral line shape relative to the
> standard
> spectrum. This mismatch between the standard spectrum and the
> analogous species can be partially accounted for by relaxing the summation
> constraint. In this case, the fitted scaling factors for the appropriate
> standards are
> renormalized to one, so they are intended to represent the approximate
> fraction of each
> species in the sample.
>
> This is part of my book chapter. The next sections show some examples. If
> you want a copy just send me an email directly and I'll send it to you.
>
> Kelly, S. D., Hesterberg, D. and Ravel, B. (2008). Analysis of soils and
> minerals using X-ray absorption spectroscopy. Methods of soil analysis,
> Part
> 5 -Mineralogical methods. Ulery, A. L. and Drees, L. R. Madison, WI, USA,
> Soil Science Society of America: 367-463.
>
>
> Cheers,
> Shelly
> dr.sdkelly at gmail.com
>
>
> On Tue, May 10, 2011 at 12:01 AM, Saugata Datta
> <saugatadatta at hotmail.com>wrote:
>
>> Dear Iffefit group.,
>>
>> I am just starting to know this forum, and I read some messages from
>> time
>> to time and find it very useful., I have a question on the Linear
>> Combination Fitting--using to fit my sample with a few standards.
>> I am experiencing that on some iterations of the fit (which gives good
>> reduced chi square value, / good R Factor values) but shows the
>> following,
>> as an example:
>> Standard Weight E0
>> X 0.267(0.056) 0
>> Y 0.249 (0.017) 0
>> M 0.220 (0.015) 0
>> N 0.428 (0.055) 0
>> P 0.000 (0.082) 0
>>
>> Now, I am confused about this "P" standard...as it shows 0.000 (weight);
>> should I even choose this iteration, or will go to the the next one?
>>
>> And the next question is: if the addition of all weigths is 0.999 or
>> 1.164
>> --- can I consider them? What I mean is: what is the range of acceptance
>> of
>> sum of all weights (I am chqing the check box for force weights to sum
>> to
>> 1)?
>>
>> thanks for your anticipated help.
>>
>> saugata
>>
>>
>>
>>
>>
>> > Date: Mon, 9 May 2011 15:19:05 -0700
>> > From: garcia.ff.000 at gmail.com
>> > To: ifeffit at millenia.cars.aps.anl.gov
>> > Subject: [Ifeffit] Linux command line ff2chi yields no output
>> >
>> > Dear users,
>> >
>> > I was able to install iffefit on linux. From the command line I run:
>> >
>> > feff6 feff.inp
>> >
>> > This worked fine and several feffnnnn.dat files were generated. Then,
>> > I wrote an input script, tmp.iff (shortened list of paths here), for
>> > ifeffit as follows:
>> >
>> > # tmp.iff
>> >
>> > path(1, file=feff0001.dat, s02 = 0.9, sigma2 = 0 .001)
>> > path(2, file=feff0002.dat, s02 = 0.9, sigma2 = 0 .001)
>> > path(3, file=feff0003.dat, s02 = 0.9, sigma2 = 0 .001)
>> > path(4, file=feff0004.dat, s02 = 0.9, sigma2 = 0 .001)
>> > path(5, file=feff0005.dat, s02 = 0.9, sigma2 = 0 .001)
>> > path(6, file=feff0006.dat, s02 = 0.9, sigma2 = 0 .001)
>> > path(7, file=feff0007.dat, s02 = 0.9, sigma2 = 0 .001)
>> > path(8, file=feff0008.dat, s02 = 0.9, sigma2 = 0 .001)
>> > path(9, file=feff0009.dat, s02 = 0.9, sigma2 = 0 .001)
>> > path(10, file=feff0010.dat, s02 = 0.9, sigma2 = 0 .001)
>> > path(11, file=feff0011.dat, s02 = 0.9, sigma2 = 0 .001)
>> >
>> > ff2chi(1-11, group=mycalc)
>> >
>> > fftf(mycalc.chi, kmin=1, kmax=15, dk=0.5, kweight=2.0,
>> kwindow='hanning')
>> >
>> > #
>> >
>> > My aim here is to sum the paths to generate chi(k). Now if I run the
>> > following command:
>> >
>> > ifeffit -x tmp.iff
>> >
>> > the following output is printed on the screen:
>> >
>> > reading feff0101.dat
>> > reading feff0102.dat
>> > reading feff0103.dat
>> > reading feff0104.dat
>> > reading feff0105.dat
>> > reading feff0106.dat
>> > reading feff0107.dat
>> > reading feff0108.dat
>> > reading feff0109.dat
>> > reading feff0001.dat
>> > reading feff0002.dat
>> > reading feff0003.dat
>> > reading feff0004.dat
>> > reading feff0005.dat
>> > reading feff0006.dat
>> > reading feff0007.dat
>> > reading feff0008.dat
>> > reading feff0009.dat
>> > reading feff0010.dat
>> > reading feff0011.dat
>> >
>> > It appears that the feffnnnn.dat files were read successfully.
>> > However, no mycalc.chi output was produced by ff2chi() [and therefore
>> > no mycalc.chir_* output was produced by fftf()]. I don't know if my
>> > approach is missing an important step or my entire procedure is
>> > nonsensical.
>> >
>> >
>> > Thanks a lot!
>> > _______________________________________________
>> > Ifeffit mailing list
>> > Ifeffit at millenia.cars.aps.anl.gov
>> > http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
>>
>>
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>>
>>
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--
Christoph Sahle
Technische Universität Dortmund
Experimentelle Physik I
Otto-Hahn-Strasse 4
44221 Dortmund
Germany
Tel.: 0231-755-3759
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