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 pl...@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-boun...@zeus.theochem.tuwien.ac.at
[wien-boun...@zeus.theochem.tuwien.ac.at]" im Auftrag von
"pl...@physics.ucdavis.edu [pl...@physics.ucdavis.edu]
Gesendet: Freitag, 13. Dezember 2013 18:02
An: wien@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, pl...@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, pl...@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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-----------------------------------------
Peter Blaha
Inst. Materials Chemistry, TU Vienna
Getreidemarkt 9, A-1060 Vienna, Austria
Tel: +43-1-5880115671
Fax: +43-1-5880115698
email: pbl...@theochem.tuwien.ac.at
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