[Wien] Calculation spin-orbit coupling with two different approach gives different results

[Peter Blaha]

It is well know that GGA+U calculations can end up in different states 
(see previous posts).

If you have used the same parameters, you should use the total energies 
of the two calculations and the one with lower energy should be the 
better one (but not necessarily the best !)

In any case, I always recommend:

First do a standard GGA calculation (also check forces, if they are small).
Then add SO and do a GGA+SO calculation (if you really have heavy elements?)
x lapwdm -up -so      to generate density matrices

and finally add the "U" and do   GGA+so+U

There is, however, no guarantee that you find the lowest energy ground 
state !  Sometimes it is good to start with a smaller U-value than 
anticipated.
Sometimes you may do a structure relaxation at the GGA-level and use 
this structure,
or a structure relaxation at GGA+U (no SO).

If SO is not a major effect, I'd first do everything without SO.

-------------------
 From these advices you can see that there is not a unique and save way, 
which works in all cases.



On 11/23/2015 12:10 PM, Santu Baidya wrote:
> Dear Prof. Blaha and wien2k users,
>
>       I use wien2k version WIEN2k_14.1. Recently I did spin-orbit
> coupling calculation under GGA+U+SOC approximation with two different
> approaches- one starting from collinear ground state and another
> starting from scratch (random wavefunction). Two approaches give me
> completely different results -metal and insulator.
>
> Please tell me which approach should I accept as solution.
>
> I look forward to get reply.
>
> Thanking you,
>
> Santu Baidya
> University of Duisburg-Essen
> Duisburg
>
>
>
>
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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