[Wien] Slab symmetry with SOC
Peter Blaha
pblaha at theochem.tuwien.ac.at
Sat Dec 14 15:00:30 CET 2013
So nn and sgroup did the correct job. The atoms on opposite sides
of the slab should be equivalent.
Why do you think that SO should split atoms on the two sides of the slab ???
Without doing the calculation, I expect that for (001) direction there should be no change,
while for (100) direction there is no splitting of atoms, but lower symmetry ???
Am 14.12.2013 14:48, schrieb pluto at physics.ucdavis.edu:
> Dear Prof. Blaha, dear Gerhardt,
>
> Prof. Blaha, thank you for this detailed procedure :-)
>
> I tried this today. What happens, is that nn and sgroup create *.struct
> file with space group 123, and 8 unique atoms (15 atoms total). The atoms
> on the opposite sides of the slab are merged into a single unique
> position.
>
> Calculation with SOC needs to have the atoms on the opposite sides of the
> slab splitted. However, initso_lapw does not split anything, and the
> *.struct (and *.struct_so) file stays pretty much the same as before, at
> least it again has only 8 unique atoms (15 total). As a result, after
> running SCF with SOC and sp I will not be able to separate the surface
> electronic structures on the opposite sites of the slab (along the
> in-plane axis orthogonal to the magnetization they will differ).
>
> Is it allowed/possible to use a primitive cell, and manually include the
> 2-fold rotation axis (which would be identical to the magnetization axis)?
>
> Regards,
> Lukasz
>
>
>
> On 12/13/2013 8:38 PM, Peter Blaha wrote:
>> Lets start "systematic". There's nothing simpler than creating
>> a (001) surface:
>>
>> Forget spin-orbit at the moment, just create a slab.
>>
>> Take a unit cell of bcc-Fe and
>>
>> x supercell with 1x1x7, add vacuum in z (eg. 30 bohr, your 15 bohr are
> a little too small)
>> and "repeat atom at z=0".
>>
>> Take the resulting struct file and run "several times"
>> x nn (always accept the created struct file).
>> x sgroup (sgroup will shift for you the positions, so that
>> you have a symmetric slab with inversion symmetry.
>> accept the struct file from sgroup).
>>
>> You can now do:
>>
>> init_lapw -b -sp -numk 400 (maybe with fermit 0.004, because we have
>> a 2D BZ and TETRA may have problems).
>> runsp -fc 1 converge and optimize positions (MSR1a).
>>
>> save_lapw
>>
>> Now you can run initso_lapw
>> Define magnetization direction and say "spin-polarization" yes.
>> This runs symmetso and depending on the direction of M it may/may not
>> reduce symmetry. Accept the structure and run
>>
>> runsp -I -so
>>
>>
>> Am 13.12.2013 18:28, schrieb pluto at physics.ucdavis.edu:
>>> Dear Gerhard,
>>>
>>> Thank you for your comment.
>>>
>>> I have a feeling, that my system has an inversion symmetry from the point
>>> of view of the electronic structure. If you think of surface electronic
>>> structure and surface Brillouin zone, then the surface electronic
>>> structures on both sides of the slab must be the same, only inverted with
>>> respect to surface-Gamma. The inversion is there, because in my particular
>>> case electronic structure is the same along the magnetization-axis and
>>> along minus-magnetization-axis.
>>>
>>> In any case (with or without inversion symmetry) the 180deg rotation
>>> around the magnetization axis is one of the symmetry operations of my
>>> slab. How can I include it in my calculation using the w2web interface?
>>>
>>> Regards,
>>> Lukasz
>>>
>>>
>>>
>>> SO has no inversion symmetry
>>> Think about the spin when you apply an inversion.
>>>
>>> Ciao
>>> Gerhard
>>>
>>> DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
>>> "I think the problem, to be quite honest with you,
>>> is that you have never actually known what the question is."
>>>
>>> ====================================
>>> Dr. Gerhard H. Fecher
>>> Institut of Inorganic and Analytical Chemistry
>>> Johannes Gutenberg - University
>>> 55099 Mainz
>>> ________________________________________
>>> Von: wien-bounces at zeus.theochem.tuwien.ac.at
>>> [wien-bounces at zeus.theochem.tuwien.ac.at]" im Auftrag von
>>> "pluto at physics.ucdavis.edu [pluto at physics.ucdavis.edu]
>>> Gesendet: Freitag, 13. Dezember 2013 18:02
>>> An: wien at zeus.theochem.tuwien.ac.at
>>> Betreff: Re: [Wien] Slab symmetry with SOC
>>>
>>> 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
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Wien mailing list
>>>>> Wien at zeus.theochem.tuwien.ac.at
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>>>>> SEARCH the MAILING-LIST at:
>>> http://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/index.html
>>>
>>>
>>> --
>>> Dr. Lukasz Plucinski
>>> _______________________________________________
>>> Wien mailing list
>>> Wien at zeus.theochem.tuwien.ac.at
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>>>
>>>
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>
>
--
-----------------------------------------
Peter Blaha
Inst. Materials Chemistry, TU Vienna
Getreidemarkt 9, A-1060 Vienna, Austria
Tel: +43-1-5880115671
Fax: +43-1-5880115698
email: pblaha at theochem.tuwien.ac.at
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