[Wien] [SPAM?] How to obtain ELNES simulation results consistent with experiments ?

[Peter Blaha]

I do not understand your statement:

 > 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


Of course, only atom 7 has the core hole, the other atoms of the 
supercell can contribute to screening. But only the spectrum of atom 7 
is meaningful, not that of the other O atoms. So don't sum up anything, 
just calculate the spectrum for atom 7.

On 10/15/18 1:53 PM, yfding wrote:
> 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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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
WWW:   http://www.imc.tuwien.ac.at/TC_Blaha
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