[Wien] Slab symmetry with SOC

[pluto at physics.ucdavis.edu]

Dear Prof. Blaha, dear Wien2k users,

I attach the most symmetric slab which I was able to produce. I try with
15 atoms in order to save time with testing, later I am planning to do a
larger slab. You could see that now the surface normal is <100>, I started
with <001>, but sgroup swapped axes -- but this is fine. So now the
in-plane magnetization is along <001>, and it's the same as the mirror
plane normal axis (becuase the space group is the 6_Pm with the unique
c-axis).

I believe that my system should have an inversion symmetry even with SOC.
And at the same time I believe that the two surface atoms (in this case
atom 1 and atom 15) should have their unique positions (they should not be
merged into a single position as they would without SOC).

I would appreciate the advice on how to make a spin-polarized calculation
with SOC on this slab with included inversion symmetry. So far I have a
mirror plane, so it would also be ok to only add a 2-fold 180deg rotation
around the magnetization axis.

Regards,
Lukasz





On 12/13/2013 11:22 AM, Peter Blaha wrote:
> For a spin-polarized case you should use init_so and the program
symmetso.  Symmetso should give you the proper symmetries and one should
use the struct file produced by symmetso. There should be a
classification of each of the symmetry operations of the non-so case
according to A, B or none.
>
> I can hardly comment on a specific feature without doing the slab myself.
>
> Please have a look into the lecture notes about spin-orbit coupling and
the reduction of symmetry due to so (from our web-site). There is a plot
and table for a small specific example.
>
> Hwoever, note two remarks:   sgroup is completely irrelevant for this
(as it does not know about spin-orbit).
>
> symmetso is obviously not as much tested as sgroup or symmetry. So be
sure to use the latest version.
> If you have doubts about symmetso, I need the struct file and the
specific concerns.
>
> On 12/13/2013 10:00 AM, pluto at physics.ucdavis.edu wrote:
>> Dear WIEN2k experts,
>>
>> Unfortunately nobody has commented on my email below.
>>
>> I believe that in my 15-atom Fe(001) slab, with magnetization along 100
>> and SOC included, there will be a mirror 100 plane (space group 6).
>> However, I have a feeling that there are more symmetries. For example I
>> have a feeling, that there should be an inversion symmetry, or at least
>> that the 100 axis should be a two-fold rotation axis. I am not able to
>> include these symmetries.
>>
>> My calculations work well with fully primitive cell, and also with space
>> group 6 (actually sgroup rotates the slab, so that mirror plane becomes
>> 001, but this of course does not matter). But I think that in every
>> problem one should include the necessary symmetries a priori, not only to
>> save time, but to avoid some spurious results.
>>
>> Could you please give me at least some hint? I could also send my slab if
>> necessary.
>>
>> Regards,
>> Lukasz
>>
>>
>>
>>
>>
>> On 12/5/2013 10:03 AM, pluto at physics.ucdavis.edu wrote:
>>
>> Dear WIEN2k experts,
>>
>> I am calculating 29-atom Fe(001) slab with SOC with easy axis along [100].
>>
>> Without SOC one can find more symmetries, and one has only 15 inequivalent
>> atoms. However, when performing the calculation with such slab the results
>> are different compared to the complex calculation with "pure" slab of 29
>> atoms. I believe that the correct result in this calculation is that
>> surface bands along [100] and [-100] are the same, and bands along [010]
>> and [0-10] are different. So one should have 3 slightly different set of
>> surface bands: along [100] (identical to [-100]), [010], and [0-10].
>>
>> Of course on the opposite surfaces of the slab things will have the
>> inversion symmetry.
>>
>> I believe that one of the programs, e.g. symmetso should in principle be
>> able to find out, whether the symmetries are correct or not, and produce
>> the correct struct file, which is possibly a bit more symmetric than the
>> original file.
>>
>> Please advise.
>>
>> Regards,
>> Lukasz
>>
>>
>>
>>
>>
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-- 
Dr. Lukasz Plucinski
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