This problem haunts me for nearly a year, and my questions are still unsolved
after consulting a lot of literature and mailing list.
I tried to get Oxygen K edge of the 3*3*3 SrCrO3 supercell.
In my calculations, I first converted the SrCrO3 (space group P4/mmm) into a
SrCrO3 3*3*3 supercell (space group P1) in CrystalMaker, then transformed the
SrCrO3supercell.cif file into SrCrO3supercell.struct file under the Wien2k case
directory, labelled one oxygen atom to make this atom unique, did
initialization, and accepted all the queries from nn complaints. The
initialization parameters were as follows:
Rmt: Sr:2.40 Cr:1.78 O:1.61
potential: GGA of PBE-96
separation energy: -6.0 Ry
RKmax: 7.0
Max L in WF: 10
number of k points in the whole BZ: 5*5*5
number of k points in the irreducible wedge of the BZ: 18
Then I edited SrCrO3.inc and removed one core electron from the 7th atom, i.e.
1st Oxygen atom 1s state. Next I changed 0.0 to -1.0 in SrCrO3.inm. Then run
SCF in parallel (energy convergence 0.0001 Ry).
Then,
-edited case.innes :
SrCrO3 O K edge
7 (atom)
1, 0 (n, l core)
532 (E-Loss of 1st edge in eV)
200 (energy of the incident electrons in keV)
-5.0 20.0 0.1 (minimum energy, energy step, maximum energy)
0.37 0.75 (collection semiangle, convergence semiangle, both in mrad)
50 1 (NR, NT, defining the integration mesh in the detector plane)
0.7 (spectrometer broadening in eV)
OUTPUT
0 (full output)
DETECTOR POSITION
0.0 0.0 (thetax, thetay)
MODUS
energy (dscs wrt what?)
ORIENTATION SENSITIVE
0.0 0.0 0.0
SELECTION RULE
n (selection rule)
LSELECTION RULE
d
INITIALIZATION
y y (dos and xdos handling)
y y (handling of rotation matrices)
QGRID
U
END
- x lapw1
- x lapw2 -qtl
- x qtl -telnes
- x telnes3
- x broadening
As it is supercell, I calculated every peak of unequivalent O K edge and summed
them. I'm not sure all the steps I have done are right. The result is different
from the TEM EELS experiment (The O K edge EELS spectra were studied on an JEOL
ARM200F Cs-corrected TEM with a FEG and a Gatan parallel electron-energy-loss
spectroscope). The relative strength and position of the peaks are completely
inconsistent.
It's not just this example, but I've had the same problem with all the other
materials. I thought about all the possible reasons, and looked up lots of
literature and mailing lists, but I couldn't get the calculation results closer
to the experiment. I want to know how to obtain ELNES simulation results
consistent with experiments ?
Any comment(s) would be highly appreciated. Thanks in advance!
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