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

[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
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
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
>> 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
>>
>
>
>
> --
> 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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