[Wien] A few (more) elementary -so questions (with onsite -eece)

Tue May 5 19:31:31 CEST 2015

I would be interested in clarification from others, but from what I can see
in the code it appears that this is the spin direction that is used, not
just the direction of breaking the symmetry. I may be wrong.

On Tue, May 5, 2015 at 11:47 AM, pieper <pieper at ifp.tuwien.ac.at> wrote:

> I definitely am not an expert for -so, therefore I will not shoot down
> anything, only a comment:
>
>  From my point of view from magnetism I would ask for some caution with
> identifying the direction given in .inorb and .inso with 'the spin
> direction'. As Gerhard pointed out earlier in this thread, it's all
> about symmetry: The specified direction only sets up the symmetry of the
> case to be compatibel with whatever has a rotational invariance with
> that (quantization) axis - be that a spin, or orbital moment,
> magnetization, a magnetic field, ... The symmetry of the basis has to
> allow for a magnetization otherwise it won't appear when you calculate
> expectation values. Personally I find Pavel's 'lecture on spin-orbit.ps'
> here in the Wien documentation files (I hope it's still there) very
> illuminating.
>
>
>
> ---
> Dr. Martin Pieper
> Karl-Franzens University
> Institute of Physics
> Universitätsplatz 5
> A-8010 Graz
> Austria
> Tel.: +43-(0)316-380-8564
>
>
> Am 05.05.2015 14:51, schrieb Laurence Marks:
> > Me a culpa, I should have checked the mailing list first for the
> > answers.
> >
> > That said, this issue has come up enough times in the past that I
> > think the UG should be tweaked so it is clearer. Let me try my
> > interpretation, so I can be shot down if needed.
> >
> > Within Wien2k magnetic effects can be approximately included in a
> > number of ways. Some such as the spin-orbit coupling assume a
> > direction for the spin vector (for all electrons actively considered),
> > others such as Bext in orb specify a direction for an applied magnetic
> > field (in Tesla) and use the same direction for the spin vector. (The
> > two spin states are then either parallel or anti parallel to the
> > specified direction.) When a direction is specified in case.inso or
> > case.inorb this fixes the spin vector and (if used) the external
> > magnetic field direction. Via the output files from lapwdm
> > (case.scfdmXX) one can monitor how the angular momentum changes [1].
> > By using different directions for the spin vector (and field) one can
> > probe how the energy changes and/orbital occupancies with assumed
> > directions for the spin/external magnetic field.
> >
> > To escape the assumption that the spin vectors all have one direction
> > the Wienncm code has to be used.
> >
> > [1] My addendum. Changes in the occupancies can be a soft electronic
> > mode, i.e. very small changes in the energy for quite large changes in
> > the density. The older mixing algorithms (MSEC1 or MSEC3) are not so
> > good for soft modes and can stagnate. MSR1 is better and the next
> > release (7.0) is much better. With onsite -eece &/or -orb it may help
> > to "push" the mixer by either forcing a larger step (echo .2 > .msec
> > or echo .1 > .pratt) or stopping, doing a force on the orbital
> > potential (x orb -up; x orb -dn) then restarting with -NI. It is
> > probably wise to check how the orbital momentum is converging (grep
> > :ORB0 *.scf, perhaps other) and make sure that the mixing is not
> > starving (grep GREED: *.scf and check the values are not small, e.g.
> > 0.035).
> >
> > ___________________________
> >  Professor Laurence Marks
> >  Department of Materials Science and Engineering
> >  Northwestern University
> >  www.numis.northwestern.edu [1]
> >  MURI4D.numis.northwestern.edu [2]
> >  Co-Editor, Acta Cryst A
> >  "Research is to see what everybody else has seen, and to think what
> > nobody else has thought"
> >  Albert Szent-Gyorgi
> > On May 4, 2015 6:22 PM, "Laurence Marks" <L-marks at northwestern.edu>
> > wrote:
> >
> >> Typo:
> >>
> >> "although I remember don't symmetry operations being split into
> >> these two classes everywhere in the code"
> >>
> >> On Mon, May 4, 2015 at 6:04 PM, Laurence Marks
> >> <L-marks at northwestern.edu> wrote:
> >>
> >>> I am a newbie at -so, so a few simple questions.
> >>>
> >>> a) What is the meaning of the orbital moment in case.scfdm* ? Is
> >>> that the average direction projected to the global axis system?
> >>>
> >>> b) What is the physical significance of the orbital moment being
> >>> parallel (or not quite parallel) to the direction used in
> >>> case.inso?
> >>>
> >>> c) I understand that the results for different directions of B in
> >>> case.inso reflect the magnetic anisotropy, but what are the units
> >>> of field (if any)?
> >>>
> >>> d) What else is worth looking at? The partial orbital moment
> >>> (:POM) seems relevant, but what exactly is it?
> >>>
> >>> e) I am "blindly" trusting that initso knows what it is doing, and
> >>> have left the "B" symmetry operations in case.struct (although I
> >>> remember symmetry operations being split into these two classes
> >>> everywhere in the code). This seems to conflict with Pavel's
> >>> notes, although those may be too old.
> >>>
> >>> Thanks.
> >>>
> >>> --
> >>>
> >>> Professor Laurence Marks
> >>> Department of Materials Science and Engineering
> >>> Northwestern University
> >>> www.numis.northwestern.edu [1]
> >>> Corrosion in 4D: MURI4D.numis.northwestern.edu [2]
> >>> Co-Editor, Acta Cryst A
> >>> "Research is to see what everybody else has seen, and to think
> >>> what nobody else has thought"
> >>> Albert Szent-Gyorgi
> >>
> >> --
> >>
> >> Professor Laurence Marks
> >> Department of Materials Science and Engineering
> >> Northwestern University
> >> www.numis.northwestern.edu [1]
> >> Corrosion in 4D: MURI4D.numis.northwestern.edu [2]
> >> Co-Editor, Acta Cryst A
> >> "Research is to see what everybody else has seen, and to think what
> >> nobody else has thought"
> >> Albert Szent-Gyorgi
> >
> >
> > Links:
> > ------
> > [1] http://www.numis.northwestern.edu
> > [2] http://MURI4D.numis.northwestern.edu
> >
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-- 
Professor Laurence Marks
Department of Materials Science and Engineering
Northwestern University
www.numis.northwestern.edu
Corrosion in 4D: MURI4D.numis.northwestern.edu
Co-Editor, Acta Cryst A
"Research is to see what everybody else has seen, and to think what nobody
else has thought"
Albert Szent-Gyorgi
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