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Re: Charge disproportionation and XANES in FEFF
Dear FEFF users,
I want to add to the big discussion on how to use feff for
materials with charge disproportionation, started by Scott
Calvin and Dr. Sidorenko. I will answer the questions of Scott,
since they seems to be common problem.
On Tue, 1 Jul 2003, Scott Calvin wrote:
> 1) How does one simulate charge disproportionation with FEFF?
a) Do nothing for inequivalent sites:
As Bruce Ravel wrote before, the inequivalent sites within
unit cells automatically will get different absorption and one needs
to average over them with appropriate weight (e.g tetrahedral and
octahedral sites in Fe3O4).
b) ION card: can be used to simulate charge transfer but cannot
give self-consistent results. I still suggest to use
SCF 4.0 0 1
with this card the density and potential is not changed, but the Fermi
level is found, which will make more reliable simulations.
c) Fix the number of localized electrons: currently this can be done
for f-electrons only and with feff8.2 only. Feff8.2 by default
freezes the number of f-electron to the value set in subroutine getorb
for each element. (UNFREEZEF unfix the number of f-electrons like in
feff8.1). You can edit subroutine getorb to change the number of
f-electrons and run XANES calculation for f^N
f^(N+1) f^(N-1) configurations.
You will need to average over configurations with appropriate weights.
The obvious advantage of this approach is that you can run self-consistent
calculation, unlike in case b).
Let me know, if this is what you would like to do also for d-electrons.
since it will take me some time to get a patch to freeze number of
d-electrons. For nonselfconsistent calculations you can do it right away.
> 2) Do XANES calculations without the SCF card have even qualitative
> validity, or are they completely pointless?
I think yes. For qualitative changes in XANES spectra due to different
charge or number of localized (d,f) electrons, you can do calculation
with SCF 4.0 0 1. (see above).
> 3) Why am I getting an error?
Your input file also did not work on my computer. I did few changes
to your file and attached modified feff.inp to this message.
The most crucial thing was to add correct stoichiometry in
POTENTIAL cards, which is the 6-th column below.
POTENTIALS
* ipot z label
0 26 Fe -1 -1 0.01
1 8 O -1 -1 3.0
2 38 Sr -1 -1 1.0
3 26 Fe -1 -1 0.99
I changed also
RMAX 1.0
* RMAX 6.76367
FMS 5.0
since path expansion often gives negative absorption in XANES and does not
converge, it is better to use FMS calculation in XANES.
SCF 4.0 0 1
as discussed before it is a better guess of the Fermi level
I also think that your feff.inp file has too few atoms, which can
be easily fixed using ATOMS program.
With these changes program does not crash. So you can try
to see how ION card affects the simulated XANES.
Best wishes
Alexei Ankudinov
* This feff.inp file generated by ATOMS, version 2.50
* ATOMS written by and copyright (c) Bruce Ravel, 1992-1999
* -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- *
* total mu = 1032.8 cm^-1, delta mu = 541.1 cm^-1
* specific gravity = 5.339, cluster contains 119 atoms.
* -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- *
* mcmaster corrections: 0.00065 ang^2 and 0.812E-06 ang^4
* -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- * -- *
TITLE name: SrFeO3
TITLE formula: SrFeO3
TITLE Simplistic based on SrTiO3
HOLE 1 1.0 Fe K edge ( 7.112 keV), second number is S0^2
* mphase,mpath,mfeff,mchi
CONTROL 1 1 1 1
* PRINT 1 0 0 0 0 3
RMAX 1.0
* RMAX 6.76367
*CRITERIA curved plane
*DEBYE temp debye-temp
*NLEG 8
XANES
FMS 5.0
SCF 4.0 0 1
POTENTIALS
* ipot z label
0 26 Fe -1 -1 0.01
1 8 O -1 -1 3.0
2 38 Sr -1 -1 1.0
3 26 Fe -1 -1 0.99
ION 0 0.4
ION 1 -0.2
ION 2 0.2
ION 3 0.4
* SCF 3.0
ATOMS
0.00000 0.00000 0.00000 0 Fe1 0.00000
-1.95250 0.00000 0.00000 1 O1 1.95250
0.00000 0.00000 -1.95250 1 O1 1.95250
0.00000 -1.95250 0.00000 1 O1 1.95250
0.00000 0.00000 1.95250 1 O1 1.95250
0.00000 1.95250 0.00000 1 O1 1.95250
1.95250 0.00000 0.00000 1 O1 1.95250
-1.95250 1.95250 -1.95250 2 Sr1 3.38183
-1.95250 -1.95250 1.95250 2 Sr1 3.38183
-1.95250 1.95250 1.95250 2 Sr1 3.38183
-1.95250 -1.95250 -1.95250 2 Sr1 3.38183
1.95250 1.95250 1.95250 2 Sr1 3.38183
1.95250 -1.95250 -1.95250 2 Sr1 3.38183
1.95250 1.95250 -1.95250 2 Sr1 3.38183
1.95250 -1.95250 1.95250 2 Sr1 3.38183
-3.90500 0.00000 0.00000 3 Fe1 3.90500
0.00000 -3.90500 0.00000 3 Fe1 3.90500
0.00000 3.90500 0.00000 3 Fe1 3.90500
0.00000 0.00000 3.90500 3 Fe1 3.90500
0.00000 0.00000 -3.90500 3 Fe1 3.90500
3.90500 0.00000 0.00000 3 Fe1 3.90500
-3.90500 1.95250 0.00000 1 O1 4.36592
-3.90500 -1.95250 0.00000 1 O1 4.36592
-3.90500 0.00000 1.95250 1 O1 4.36592
-3.90500 0.00000 -1.95250 1 O1 4.36592
-1.95250 -3.90500 0.00000 1 O1 4.36592
-1.95250 0.00000 3.90500 1 O1 4.36592
-1.95250 3.90500 0.00000 1 O1 4.36592
-1.95250 0.00000 -3.90500 1 O1 4.36592
0.00000 1.95250 -3.90500 1 O1 4.36592
0.00000 3.90500 -1.95250 1 O1 4.36592
0.00000 -3.90500 1.95250 1 O1 4.36592
0.00000 -3.90500 -1.95250 1 O1 4.36592
0.00000 3.90500 1.95250 1 O1 4.36592
0.00000 -1.95250 -3.90500 1 O1 4.36592
0.00000 1.95250 3.90500 1 O1 4.36592
0.00000 -1.95250 3.90500 1 O1 4.36592
1.95250 3.90500 0.00000 1 O1 4.36592
1.95250 0.00000 -3.90500 1 O1 4.36592
1.95250 0.00000 3.90500 1 O1 4.36592
1.95250 -3.90500 0.00000 1 O1 4.36592
3.90500 1.95250 0.00000 1 O1 4.36592
3.90500 0.00000 -1.95250 1 O1 4.36592
3.90500 -1.95250 0.00000 1 O1 4.36592
3.90500 0.00000 1.95250 1 O1 4.36592
-3.90500 3.90500 0.00000 3 Fe1 5.52250
-3.90500 0.00000 3.90500 3 Fe1 5.52250
-3.90500 -3.90500 0.00000 3 Fe1 5.52250
-3.90500 0.00000 -3.90500 3 Fe1 5.52250
0.00000 3.90500 3.90500 3 Fe1 5.52250
0.00000 -3.90500 3.90500 3 Fe1 5.52250
0.00000 3.90500 -3.90500 3 Fe1 5.52250
0.00000 -3.90500 -3.90500 3 Fe1 5.52250
3.90500 0.00000 -3.90500 3 Fe1 5.52250
3.90500 0.00000 3.90500 3 Fe1 5.52250
3.90500 -3.90500 0.00000 3 Fe1 5.52250
3.90500 3.90500 0.00000 3 Fe1 5.52250
-5.85750 0.00000 0.00000 1 O1 5.85750
-3.90500 1.95250 -3.90500 1 O1 5.85750
-3.90500 -1.95250 -3.90500 1 O1 5.85750
-3.90500 -1.95250 3.90500 1 O1 5.85750
-3.90500 -3.90500 1.95250 1 O1 5.85750
-3.90500 3.90500 -1.95250 1 O1 5.85750
-3.90500 3.90500 1.95250 1 O1 5.85750
-3.90500 -3.90500 -1.95250 1 O1 5.85750
-3.90500 1.95250 3.90500 1 O1 5.85750
-1.95250 -3.90500 -3.90500 1 O1 5.85750
-1.95250 3.90500 -3.90500 1 O1 5.85750
-1.95250 3.90500 3.90500 1 O1 5.85750
-1.95250 -3.90500 3.90500 1 O1 5.85750
0.00000 -5.85750 0.00000 1 O1 5.85750
0.00000 0.00000 -5.85750 1 O1 5.85750
0.00000 5.85750 0.00000 1 O1 5.85750
0.00000 0.00000 5.85750 1 O1 5.85750
1.95250 3.90500 -3.90500 1 O1 5.85750
1.95250 3.90500 3.90500 1 O1 5.85750
1.95250 -3.90500 3.90500 1 O1 5.85750
1.95250 -3.90500 -3.90500 1 O1 5.85750
3.90500 1.95250 -3.90500 1 O1 5.85750
3.90500 1.95250 3.90500 1 O1 5.85750
3.90500 -3.90500 1.95250 1 O1 5.85750
3.90500 -1.95250 -3.90500 1 O1 5.85750
3.90500 3.90500 1.95250 1 O1 5.85750
3.90500 -1.95250 3.90500 1 O1 5.85750
3.90500 -3.90500 -1.95250 1 O1 5.85750
3.90500 3.90500 -1.95250 1 O1 5.85750
5.85750 0.00000 0.00000 1 O1 5.85750
-5.85750 -1.95250 -1.95250 2 Sr1 6.47571
-5.85750 1.95250 -1.95250 2 Sr1 6.47571
-5.85750 -1.95250 1.95250 2 Sr1 6.47571
-5.85750 1.95250 1.95250 2 Sr1 6.47571
-1.95250 -5.85750 -1.95250 2 Sr1 6.47571
-1.95250 -1.95250 5.85750 2 Sr1 6.47571
-1.95250 5.85750 1.95250 2 Sr1 6.47571
-1.95250 -1.95250 -5.85750 2 Sr1 6.47571
-1.95250 -5.85750 1.95250 2 Sr1 6.47571
-1.95250 5.85750 -1.95250 2 Sr1 6.47571
-1.95250 1.95250 -5.85750 2 Sr1 6.47571
-1.95250 1.95250 5.85750 2 Sr1 6.47571
1.95250 -5.85750 1.95250 2 Sr1 6.47571
1.95250 -1.95250 -5.85750 2 Sr1 6.47571
1.95250 1.95250 5.85750 2 Sr1 6.47571
1.95250 -1.95250 5.85750 2 Sr1 6.47571
1.95250 5.85750 -1.95250 2 Sr1 6.47571
1.95250 1.95250 -5.85750 2 Sr1 6.47571
1.95250 5.85750 1.95250 2 Sr1 6.47571
1.95250 -5.85750 -1.95250 2 Sr1 6.47571
5.85750 1.95250 1.95250 2 Sr1 6.47571
5.85750 -1.95250 -1.95250 2 Sr1 6.47571
5.85750 -1.95250 1.95250 2 Sr1 6.47571
5.85750 1.95250 -1.95250 2 Sr1 6.47571
-3.90500 3.90500 -3.90500 3 Fe1 6.76366
-3.90500 3.90500 3.90500 3 Fe1 6.76366
-3.90500 -3.90500 -3.90500 3 Fe1 6.76366
-3.90500 -3.90500 3.90500 3 Fe1 6.76366
3.90500 -3.90500 -3.90500 3 Fe1 6.76366
3.90500 -3.90500 3.90500 3 Fe1 6.76366
3.90500 3.90500 -3.90500 3 Fe1 6.76366
3.90500 3.90500 3.90500 3 Fe1 6.76366
END