[Wien] Clarification on (a) effective moment including spin-orbit coupling and (b) spin-state configuration

[tran at theochem.tuwien.ac.at]

As I said, :MMTOT is the number of up-electrons minus the number of
down-electrons, which obviously means that orbital(L) is not included.

If your system is an insulator, then :MMTOT is an integer
(e.g., :MMTOT=23-18=5), but if it is a metal, then :MMTOT can be
a non-integer (e.g., :MMTOT=22.8-18.2=4.6) because some bands are
only partially filled.


On Wed, 2 Oct 2013, Kalpana wrote:

> Dear Prof. Blaha and Tran,    Thanks for your nice comment.
> Your reply to my first and third questions in clear now.
> However, I am still not clear to my first question.
> 
> While performing the calculations for GGA+U and GGA+U+SOC, I obtained solutions of total spin-magnetic moemnts as below:
>       With GGA+U             ==== :MMTOT: SPIN MAGNETIC MOMENT IN CELL   = 5.00042
>       With GGA+U+SOC  ==== :MMTOT: SPIN MAGNETIC MOMENT IN CELL   =     4.72942
> 
> (i) The MMTOT (Spin-magnetic moment) from GGA+U+SOC is 4.72942 not 5.00, which I suppose to be same or nearly equal because both
> are spin-magnetic moment in cell [without including spin-orbit coupling]. 
> So, I am interested to know whether the SPIN MAGNETIC MOMENT in CELL for GGA+U+SOC should be read as an effective moment [i.e.
> spin(S) + orbital (L)] or something else.
> Additionally, if they are the actual SPIN MOMENT in GGA+U+SOC, why are their magnitude different with GGA+U because
> orbital-moment is not included. 
> Can you please clarify my doubt again.
> Thanks
> Kalpana
> 
> 
> 
> 
> 
> 
> On Wed, Oct 2, 2013 at 9:36 PM, Peter Blaha <pblaha at theochem.tuwien.ac.at> wrote:
>             (ii) When considering the GGA+U+SOC (spin-orbit coupling), I find that
>             the results on spin-magnetic moment in a cell significantly changes with
>             respect to GGA+U.
>             For example,
>             With GGA+U             ==== :MMTOT: SPIN MAGNETIC MOMENT IN CELL   =
>             5.00042
>             With GGA+U+SOC  ==== :MMTOT: SPIN MAGNETIC MOMENT IN CELL   =     4.72942
> 
> 
> If you did not make any other mistake, it means that without SO you have probably an insulating state, while with SO you
> got a metal.
>
>       Co
>       Ar 3
>       3, 2,2.0  N
> 3, 2,2.0  N   intermediate spin:    low spin
> 3,-3,3.0  N      2.0                  1.5
> 3,-3,0.0  N      1.0                  1.5
> 4,-1,1.0  N
> 4,-1,1.0  N--
> 
> 
> But there is NO guarantee, that these starting configurations yield the desired states.
> 
> Evendually, you can manually modify the case.dmatup/dn files and run
> -orbc   or for a FM you can use runfsm
> 
> Peter Blaha
> Inst.Materials Chemistry
> TU Vienna
> Getreidemarkt 9
> A-1060 Vienna
> Austria
> +43-1-5880115671
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>