[Wien] inversion and spin-orbit

[Peter Blaha]

Hi,

The code should do it right.(Make sure you use the most recent version, 
there was some change/fix recently).

Since your GaAs is a non-magneitc (non-spinpolarized) calculation, time 
inversion acts like space inversion and is used when generating the k-mesh.

In fact, eigenvalues are identical, but eigenfunctions at +k and -k have 
opposite spin, but since we do not care here about spin, there is no 
need to calculate both, +k and -k.

This is of course different in a spin-polarized system. Here you cannot 
add inversion symmetry when generating the k-mesh. This is done in 
initso_lapw by selecting "spin-polarization", and later on by the -so 
switch to kgen.

Regards

On 3/13/19 10:03 AM, Mikhail Nestoklon wrote:
> Dear wien2k community,
> I do not fully understand the way kgen (and code in general) treats the 
> structures
> without inversion.
> For standard GaAs structure, spacegroup #216, without inversion, when I do
> calculations WITH spin-orbit, the kgen
> $ x kgen -so
> still informs that
> """
> 
> GaAs.ksym not present, using GaAs.struct because inversion is present
> 24 symmetry operations without inversion
> inversion added (non-spinpolarized non-so calculation)
> 
> """
> In fact, there is no inversion center in the system (and code is aware 
> of that)
> and there is spin-orbit, so the states k and -k are not the same 
> (Indeed, they
> are still connected by the time inversion, but technically it is 
> different from
> spacial inversion).
> 
> The manual is a bit cryptic about this part: It tells that the symmetry 
> is lowered
> only if the magnetic field is switched on, in which case one should 
> use symmetso.
> 
> Does this mean that "under the hood" the code behaves correctly and in fact
> uses time inversion and not spacial inversion or I should trick it into 
> removing the
> inversion from the symmetry if I do care about correct description of 
> properties
> which come from the lack of inversion center?
> 
> Thank you in advance.
> 
> Sincerely,
> Mikhail Nestoklon
> 
> 
> 
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-- 

                                       P.Blaha
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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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