[Wien] Difference between "x lapw2 -qtl" and "x qtl"

[pluto]

Dear All,

I am calculating one of the 1T TMDC materials. This material e.g. has a 
spin-polarized Dirac cone on the surface (see e.g. DOI 
10.1088/2516-1075/ab09b7 for review of similar materials).

I calculated 10L (15 inequivalent atoms) and 20L (30 inequivalent atoms) 
slabs. I allowed sgroup to find the space group (no. 164) in order to 
speed up the calculation. In this case it means each inequivalent atom 
has 2 equivalent positions.

It is a spin polarized calculation with SOC. Band structures look good 
compared to the literature Wannier calculations.

One obvious test is to check spin polarization of the Dirac cone.

Band characters can be calculated either using
x lapw2 -band -qtl -up/dn -so (default in w2web)
or using
x qtl -band -up/dn -so

Importantly, in order to make x qtl work I need to
cp case.in1 case.in1c
although the system does have inversion (otherwise qtl gives an error 
and nothing is calculated). Is this allowed?

Another problem is that for the 20L slab x spaghetti does not want to 
plot fat bands out of case.qtlup/dn produced by "x qtl". I didn't look 
at the case.qtlup/dn files in detail yet (I will, but it might take a 
while), but either they are incomplete (i.e. x qtl cannot handle a big 
slab), or spaghetti cannot handle these files beyond a certain size 
limit. On the other hand case.qtlup/dn produced by x lapw2 always work 
with fat bands. Of couse when using x qtl I limit the number of atoms in 
case.inq, and I typically only calculate characters for 2 outermost 
atoms (my case.inq pasted below). For 10L slab everything works fine.

The plotted results (using w2web) for these two cases look very 
different. I tried plotting characters on couple of outermost atoms.

x lapw2 does not show any spin polarization of the Dirac cone
x qtl shows clear very high polarization of the Dirac cone

This happens when I plot total character on a particular atom, is it not 
an effect related to some Y_lm character or things like that.

I think in general I should split all atoms in order to get correct spin 
polarization (the so-called hidden spin polarization introduced by 
Zunger/Freeman). This is what one had to do with the 2H MoS2 
calculations several years back. But splitting all atoms would probably 
make 20L slab calculation prohibitive on my system (I think 20L would be 
unrealistic).

But perhaps the QTL program can somehow do the job of splitting the 
equivalent atoms even on slab with equivalent positions.

I also paste below case.inso, note that the direction of spin 
polarization quant. axis is along 100, i.e. in-plane, as it should for 
these materials.

Best,
Lukasz


case.inq file:

-9.0   3.0           Emin  Emax
   2                 number of atoms
    1   1  0  1       iatom,qsplit,symmetrize,locrot
3   0  1  2          nL, l-values
0 0 1
   30   1  0  1       iatom,qsplit,symmetrize,locrot
3   0  1  2          nL, l-values
0 0 1

case.inso

WFFIL
4  0  0                 llmax,ipr,kpot
-10  1.9                Emin, Emax
     1 0 0                           h,k,l (direction of magnetization)
  30                       number of atoms with RLO
1 -3.53 0.0001 STOP             atom-number, E-param for RLO
2 -3.53 0.0001 STOP             atom-number, E-param for RLO
3 -3.53 0.0001 STOP             atom-number, E-param for RLO
4 -3.53 0.0001 STOP             atom-number, E-param for RLO
5 -3.53 0.0001 STOP             atom-number, E-param for RLO
6 -3.53 0.0001 STOP             atom-number, E-param for RLO
7 -3.53 0.0001 STOP             atom-number, E-param for RLO
8 -3.53 0.0001 STOP             atom-number, E-param for RLO
9 -3.53 0.0001 STOP             atom-number, E-param for RLO
10 -3.53 0.0001 STOP             atom-number, E-param for RLO
11 0.30 0.0000 CONT             atom-number, E-param for RLO
12 0.30 0.0000 CONT             atom-number, E-param for RLO
13 0.30 0.0000 CONT             atom-number, E-param for RLO
14 0.30 0.0000 CONT             atom-number, E-param for RLO
15 0.30 0.0000 CONT             atom-number, E-param for RLO
16 0.30 0.0000 CONT             atom-number, E-param for RLO
17 0.30 0.0000 CONT             atom-number, E-param for RLO
18 0.30 0.0000 CONT             atom-number, E-param for RLO
19 0.30 0.0000 CONT             atom-number, E-param for RLO
20 0.30 0.0000 CONT             atom-number, E-param for RLO
21 0.30 0.0000 CONT             atom-number, E-param for RLO
22 0.30 0.0000 CONT             atom-number, E-param for RLO
23 0.30 0.0000 CONT             atom-number, E-param for RLO
24 0.30 0.0000 CONT             atom-number, E-param for RLO
25 0.30 0.0000 CONT             atom-number, E-param for RLO
26 0.30 0.0000 CONT             atom-number, E-param for RLO
27 0.30 0.0000 CONT             atom-number, E-param for RLO
28 0.30 0.0000 CONT             atom-number, E-param for RLO
29 0.30 0.0000 CONT             atom-number, E-param for RLO
30 0.30 0.0000 CONT             atom-number, E-param for RLO
0 0      number of atoms without SO, atomnumbers