[Wien] Is there an effect of SO on the ground state

[pieper]

Of course inclusion of SO interactions may lead to another magnetic 
ground state. For example, at least in principle it certainely will do 
so if the symmetry of your Hamiltonian including SO breaks some symmetry 
of the ground state you found without SO. So you might want to look 
wether or not initso induces changes of your symmetry. However, the 
effect in whatever you are interested in might be too small to make a 
real difference.

Therefore, you also might compare typical SO interaction energies for 
elements in your structure with the energy differences between the 
ground states you worked out without SO. If you have light elements 
(small SO) and large Heisenberg exchange, then probably nothing will 
happen.

In addition you should be aware of the fact that Wien2k (or any other 
DFT program) will find (if you are lucky and everything works out) the 
ground state within the symmetry you set up during initialization. If 
you set up a hexagonal structure with some AF magnetic structure on top 
of it (maybe in a larger unit cell) your result from the scf cycle will 
have that symmetry. The actual ground state of the material you are 
interested in might be completely different. A drastic example: SO 
interaction may lead to non-collinear helical spin structures - which 
are outside the scope of standard Wien2k.


---
Dr. Martin Pieper
Karl-Franzens University
Institute of Physics
Universitätsplatz 5
A-8010 Graz
Austria
Tel.: +43-(0)316-380-8564


Am 30.10.2016 14:55, schrieb Abderrahmane Reggad:
> Thanks Dr pieper for the rich information within your answer.
> 
> Perhaps I didn't formulated my question well . I am not interesting
> exactly to the ground state energy , but to the magnetic ground state.
> As I mentionned before , I want to determine the magnetic ground state
> from 5 configurations: nm,fm, afm1,afm2 and afm3 for hexagonal crystal
> structure (NiAs structure exatly); and I want to know if the inclusion
> or not of the SO coupling affect this magnetic ground state.i.e.
> without SO , I got a magnetic ground state , and if I include the SO,
> may be this leads to another magnetic ground state.
> 
> Best regards
> 
> --
> 
> Mr:
> A.Reggad                                          
> 
> Laboratoire de Génie Physique
> Université Ibn Khaldoun - Tiaret
> 
> Algerie
> 
> 
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