[Ifeffit] Energy shift (???)

Tue Aug 19 07:05:00 CDT 2008

Hi eunsuk1986 (unfortunately you did not share your full name with us...)

I had some trouble with reading your feff.inp. Nevertheless the problem of the absolute alignment of FEFF xmu and experimental data has been the subject of earlier questions. I' am citing form a list contribution of J. Rehr (Aug 3rd 2003): "The FEFF calculation of the absolute energy is not meant to be highly accurate, and errors of several eV for K-shells of large Z atoms are not unusal. Thus you did nothing wrong in the input file. To match FEFF and experiment you *always* have to shift the FEFF absolute threshold to match experiment.". There is no way (I am aware of) to tell FEFF do this absolute shift (you can and you often need to shift the position of the Fermi level though) but you can do this with every plot program. Thus you should not worry too much about the absolute energies in your xmu but a lot about relative energies (i.e. the positions of the single resonances). 

HTH

Jakob

___________________________________________________ 
Jakob Frommer 
Soil Chemistry Group 
Institute of Biogeochemistry and Pollutant Dynamics, 
ETH Zürich 
Universitätstrasse 16, 
CHN F19 
CH - 8092 Zürich 
Tel: +41 44 632 87 58 
Fax: +41 44 633 11 18 
web: http://www.ibp.ethz.ch/research/soilchemistry

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Subject: Ifeffit Digest, Vol 66, Issue 9

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Today's Topics:

   1. Energy shift (???)

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Message: 1
Date: Mon, 18 Aug 2008 16:46:26 +0900
From: ??? <eunsuk1986 at hotmail.com>
Subject: [Ifeffit] Energy shift
To: <ifeffit at millenia.cars.aps.anl.gov>
Message-ID: <COL101-W46347AB6CA04C793B53D5FDA6E0 at phx.gbl>
Content-Type: text/plain; charset="ks_c_5601-1987"

Hi everyoneI am studying XANES at Zn K-edge in ZnO nanocrystal by using FEFF8. I wrote FEFF8 as following, and got xmu.dat. I found that there was a difference between experimental data and xmu.dat (check file) for the energy. I dont understand why the energy is shifted. I wish to adjust xmu.dat in FEFF8 to my experimental dat.  If someone knows how to do, please contact me.   * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * TITLE   name:     zincite ZnO TITLE   formula:  ZnO TITLE   sites:    Zn1,O1 TITLE   refer1:   wyckoff, vol 1, ch III, p 111 TITLE   refer2: TITLE   schoen: TITLE   notes1: EDGE      K S02       1.0 *         pot    xsph  fms   paths genfmt ff2chi CONTROL   1      1     1     1     1      1 PRINT     1      0     0     0     0      0 *         r_scf   [ l_scf  n_scf  ca ] SCF       5.03864   0      15     0.1 *         ixc  [ Vr  Vi ] EXCHANGE  2      0   0*EXAFS*RPATH     9.07729 *         kmax  [ delta_k  delta_e ] XANES     4.0 !
     0.07     0.5 *         r_fms     [ l_fms ] FMS       5.53864     0 * *RPATH     0.10000 *         emin  emax  resolution LDOS      -20    20   0.1 POTENTIALS *   ipot   z [ label   l_scmt  l_fms  stoichiometry ]       0   30    Zn     -1      -1       0       1    8    O      -1      -1       1       2   30    Zn     -1      -1       1 ATOMS   0.00000     0.00000     0.00000    0   Zn1              0.00000   0.00000     0.00000     2.06302    1   O1               2.06302  -1.95951     0.00000    -0.65148    1   O1               2.06497   0.97978    -1.69700    -0.65148    1   O1               2.06500   0.97978     1.69700    -0.65148    1   O1               2.06500   0.97978    -1.69700    -2.71450    2   Zn1              3.34788   0.97978     1.69700     2.71450    2   Zn1              3.34788   0.97978     1.69700    -2.71450    2   Zn1              3.34788   0.97978    -1.69700     2.71450    2   Zn1              3.34788
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