[Wien] Difference between "x lapw2 -qtl" and "x qtl"
pluto
pluto at physics.ucdavis.edu
Wed Mar 15 10:35:24 CET 2023
Dear Prof. Blaha, dear All,
The limit of 25 atoms in QTL is a separate problem, of course. There is
separate error when exceeding 25 atoms.
Yet another issue is the number of fat bands plotted. Default is 999,
and in this case it must be increased.
I think that QTL does something more than lapw2 -qtl. I think it is
related to the "symmetrization" explained in the QTL technical report.
However, it is not clear if this always allows a correct calculation of
spin polarization even if equivalent atoms are used. Also, if this is
the case, then it would mean QTL somehow choses one of the equivalent
atoms, and plots its character. I suspect if both equivalent atoms
connected by inversion are chosen, then spin is zero because of the
Krames degeneracy in a non-magnetic system.
I will test on bulk 2H TMDC, maybe this will clarify things.
Best,
Lukasz
PS: Both atoms are Z>50, so not light. I accepted the options during
init_so_lapw. Bands looks very much correct, so it is unlikely that
something is wrong. The material is non magnetic, only spin-momentum
locked bands can be present.
On 2023-03-15 08:51, Peter Blaha wrote:
> Well, we can only guess something because there is not enough
> information.
>
> Clearly: qtl has a limit of 25 atoms in case.inqtl
>
> It should give you a corresponding error message, so you should be
> aware of that.
> On the other hand you said you limit the number of atoms to 2 in
> case.inqtl, so this should not cause an error.
>
> I would need the struct file together with an exact description of
> what you have done and what does not work. Otherwise I cannot
> reproduce things.
>
> PS: Why are you setting RLOs for all atoms ?? It does not make sense
> for valence electrons of light atoms.
>
> PPS: I'm also surprised that SO with (100) does not break more symmetry
> ???
>
>
> Am 15.03.2023 um 01:32 schrieb pluto via Wien:
>> 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
>>
>>
>>
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