[Wien] Using option Qsplit=6 in qtl to rotate to get t2g and eg

[Peter Blaha]

Wien2k will automatically calculate the symmetry related splitting of 
the d-states.

Example 1: Octahedral (cubic) symmetry:  WIEN2k sets ISPLIT=2 in 
case.struct during initialization. This symmetry was detected by x 
symmetry and you can find the proper point group of your atoms in 
case.outputs.
Because of the ISPLIT=2, when you run   x lapw2 -qtl, the case.qtl file 
will automatically contain for an atom with eg. Oh symmetry:
s,p,d,d-eg,d-t2g,f

Please look at the header of case.qtl, where it tells you the 
decomposition of the states

Example 2.: hexagonal symmetry (as in hcp Zn,Be or Mg) In case.outputs 
you find:
pointgroup is -6m2, leading to ISPLIT=4 (see UG for definitions of ISPLIT)
and the header of case.qtl givs:
s,p,pz,pxy,d,d-z2,(d-xy,dx2-y2),(d-xz,dyz),f
So the p-states have been automatically splitted into pz and px+py, 
while the 5 dstates are splitted into 3 groups, one 1-dimensional and 2 
2-dimensional irreducible representations. Wien2k does not give you the 
"label" of the irrep (like A1g or Eg) as you are looking for, but use a 
good "group-theory character table" for pointgroup -6m2 and you will 
find the "name of the representation" (A1g,..) and the corresponding 
"basis functions" (z, x+y; z**2, xz,xz, ..) so that you can make the 
corresponding asignment between or splitted partial charges and the 
"labels".

More complicated is the calculation of "approximate symmetries" (like 
eg-t2g) in a distorted octahedron), because in that case WIEN2k cannot 
do it automatically for you, but you can combine the single orbitals in 
the PROPER coordinate system yourself. In this case the x qtl program 
can be useful since it allows to calculate the PDOS in a rotated 
coordinate frame pointing into your "approximate octahedron".

PS: In corundum structure, usually it also has ISPLIT=4 and the d-z2 
orbital corresponds to A1g....


Am 26.03.2020 um 01:31 schrieb Wasim Raja Mondal:
> Dear Wien2k experts,
>                                    I am doing DOS calculation to 
> reproduce some data for V2O3 corundum trigonal structure. In this 
> distorted structure octahedra of oxygen atoms, d orbital should be split 
> into single degenerate a1g and double degenerate eg. I have calculated 
> projected density of states and I am not finding that. So, I have 
> realized that I have to use rotation and for that I want to use QTL 
> program. So far, I have done following steps:
> 
>        1. x cif2struct
> 
>        2. init_lapw
> 
>       3. run_lapw
> 
>      4.  edited   case.inq  and used the option qsplit=6
> 
>     5. copied templet for case_cf_eg_t2g in my directory.
>     6. cp case_cf_eg_t2g to case_cf2 since my atom number V is assigned as 2
> 
>    7. Getting error.
> 
> 
> Can you suggest any solution? Is this the way to project d to a1g and eg?
> 
> Thanks in advance
> Wasim
> 
> 
> On Wed, Mar 25, 2020 at 1:49 PM Wasim Raja Mondal 
> <wasimr.mondal at gmail.com <mailto:wasimr.mondal at gmail.com>> wrote:
> 
>     Dear expert,
>                         I am trying to project out t2g and a1g states of
>     V d orbitals. For that I want to use qtl program for DOS
>     calculation. I am chosing QSPLIT=6 for unitary transformation. For
>     that I copied templet as case.cf_d_eg_t2g .
> 
>     Can you please suggest me how can I proceed next?
> 
> 
> 
>     Thanks
> 
> 
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-- 
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
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