[Ifeffit] Re xanes feff8 sulfur

[Kelly, Shelly D.]

Hi Eckard,

 

I realize that you have posted a message every month for about 3 months
in a row without any reply:  Shame on us... I will try to answer some of
your questions and maybe that will help to get some discussion going.
The energy scale in feff8 is NOT defined as you would expect it to be
for determining the absolute energy of an edge.  The energy scale in
FEFF8 is related to the difference between the energy level of the
intersist (potential level inbetween the muffin tins that represent
atoms) and the threshold energy level for the excitation of the
electron.    

 

I realize that this doesn't solve your problem, but hopefully it will
spark some discussion.

 

Cheers,

Shelly

 

 
Mon Aug 13 06:00:19 CDT 2007 
Does anybody know a person, who has experience respective the topics
xanes+feff8 and sulfur K-Edges?
I would be very thankful for an answer :-)
 
sincerely yours,
Eckhard Bosman
 

 

Tue Jul 10 10:07:38 CDT 2007 

Hello,
 
i have problems with feff-xanes calculations related to pyrite. I try to
get the k-edge of sulfur (as absorber) in FeS2. I get the edge at ~2472
eV
and i think this is wrong because i get the same energy with gypsum and
i
think there should be an energyshift related to 2472 eV. My proceeding
is
as follows:
 
calculate the atomic positions with the asymetric unit from the
http://rruff.geo.arizona.edu/AMS/amcsd.php database (Pyrite spacegroup
Pa3) respectively
http://rruff.geo.arizona.edu/AMS/xtal_data/CIFfiles/00596.cif
with "powdercell 2.4"
 
feffrun with the feff.inp-file like in the attachment
(thanks to Josh Kas for his feff-hints)
 
I started the feff-run on the one hand with 12 atoms (unitcell) and on
the
other hand with 22 atoms (14x Fe and 8x S in the cube)
 
After this i plotted from xmu.dat the absorbtion mu (column 4) as a
function of the energy (column 1). The result is in the attachment too.
 
I don't know why i get everytime the Sulfur-k-edge at the same position
(for pyrite or gypsum) respectively without energyshift related to 2472
eV.
 
many thanks for your help :-)
Ciao,
Eckhard

 

Fri Jun 15 08:48:21 CDT 2007

Hallo @all,
 
(first at all, sorry for my bad english)
 
i'm a student working on my diploma thesis (nexafs/xanes) and my job is
to
simulate with FEFF 8.4 spectra, for example absorption as a function of
energy (mu_(E)). I'm a newbie in this topic and i tried to get the
k-edge
of Sulfur for the substance gypsum (CaSO4 * 2(H2O)) and pyrite (FeS2).
I'm
interested in the XANES-range of the spectra not the EXAFS. I get
everytime my peaks at ~2472 eV for Sulfur as absorber whatever substance
i
use (gypsum, pyrite,...). There are no differences with the peak
position
on the energy-scale or shifts. I'm really confused :-( I think, there
should be differences in the spectra... I send you two feff.inp files
from
my feff-runs. My source is the mineralogy database
(http://rruff.geo.arizona.edu/AMS/amcsd.php) where i get the data for
the
unitcell. Then i put the data in the XtalDraw program to get the
positions
of the Atoms in Angstrom, by the way i get i nice 3D-View of the
unitcell
:-). Then i put the values of the positions into feff...
I simulated pyrite with 12 atoms and gypsum with 48.
I'm appreciative for every help :-)
 
ciao,
Eckhard

 

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