[Wien] Non-degenerate dxy, dyz and dxz PDOS in cubic perovskite

[Asif Ali]

Dear all

I am doing GGA calculation for ABO3 perovskite with cubic structure
(SrVO3). After using the qtl program, I am able to calculate PDOS for
dxy,dyz,dxz, dz2 and dx2-y2 separately.  However, the calculated dxy, dyz
and dxz PDOS are non-generate (do not overlap). I understand that due to
crystal symmetry the PDOS should be degenerate for these three.

I read here
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg08943.html,
but i am not able to understand why dx, dyz and dxz should not be
degenerate. Please help me with this.

Regards
Asif
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Re: [Wien] Non-degenerate dxy, dyz and dxz PDOS in cubic perovskite

[Peter Blaha]

We are using a k-mesh consisting of points only in the irreducible part 
of the BZ (IBZ). Therefore this set of k-points does not contain the 
full cubic symmetry, but a symmetrization is necessary.


This is done automatically in lapw2, and thus you should use   x lapw2 
-qtl  to produce the properly symmetrized partial charges + PDOS.
You will see, that lapw2 produces only a eg and t2g PDOS, since they 
correspond to the 2 irreducible representations for d-states in cubic 
symmetry. If you want eg. the d-z2 PDOS (which does not really make 
sense, since this is not a irreducible representation), it is simply 1/2 
of the eg-PDOS.


If you want to use the qtl program, you have to do this symmetrization 
yourself. Add up the d-z2 and d-x2-y2PDOS and you get the eg-PDOS. Only 
the sum is meaningful, not the individual contributions.


If you don't believe me, just create a k-mesh in the full-BZ  (x kgen 
-fbz). after x lapw1; x qtl can now produce qtls (and PDOS) which 
fulfills your expectations. But of course, the computer time is ~20 
times bigger and the results are identical to the symmetrized ones.



Am 03.01.2022 um 14:03 schrieb Asif Ali:

Dear all

I am doing GGA calculation for ABO3 perovskite with cubic structure 
(SrVO3). After using the qtl program, I am able to calculate PDOS for 
dxy,dyz,dxz, dz2 and dx2-y2 separately.  However, the calculated dxy, 
dyz and dxz PDOS are non-generate (do not overlap). I understand that 
due to crystal symmetry the PDOS should be degenerate for these three.


I read here 
https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg08943.html 
, 
but i am not able to understand why dx, dyz and dxz should not be 
degenerate. Please help me with this.


Regards
Asif


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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
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