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

[pieper]

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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