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

[Santu Baidya]

Dear Prof. Blaha,

  Thank you very much for you reply on this. Actually I did relax the
structure under GGA+U approximation. Then took two approaches.  In one case
I did SCF calculation under GGA+U with relaxed structure  and added SOC
afterthat. In other case I took relaxed structure and did GGA+U+SOC
calculation.
Which gave me two different electronic structure for the same relaxed
structure.

So I have to take lowest energy structure.

Thanking you and regards,

Santu Baidya





On 23 November 2015 at 18:58, Peter Blaha <pblaha at theochem.tuwien.ac.at>
wrote:

> 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
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
> Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
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