[Wien] Questions about "-orbc" calculations

[Peter Blaha]

"Assumed magnetic order"  means  ferromagnetic, or a certain type of 
anti-feromagnetic order (there are many possibilities !)

And with SO you could put the magnetization (case.inso) in various 
different crystallographic directions ....

On 03/08/2013 04:40 PM, Hongbin Zhang wrote:
>
> Dear Prof. Blaha,
>
> Thank you for your reply!
>
> I suppose by "assumed magnetic order and also on the direction of the
> magnetization" you mean equivalent magnetic ordering/magnetization
> directions for a given structure. But I do not see the reason why this
> is relevant. For instance, the system I am considering now is Sr2IrO4,
> where the magnetic structure has determined experimentally and fixed
> due to the rotation of IrO6 octahedra. Yes there are many different
> ways to chose the unit cell, and I think once the structure is chosen,
> the magnetization configuration is chosen too. Maybe I should try to
> force the magnetization direction to be aligned along different
> directions to see whether it will converge (to a "correct" solution).
>
> Yes, with large U I could get convergence, but the physics is different
> from expected.
>
> Regards,
>
> Hongbin
> On Fri, 8 Mar 2013, Peter Blaha wrote:
>
>> I have done once some test calculations on some iridates.
>>
>> As far as I remember, everything depends on the assumed magnetic order
>> and also on the direction of the magnetization (with SO). Some
>> magnetic structures are easy to converge, others will not (or very
>> hard) converge.
>>
>> With LDA+U and -orbc you can often enforce a particular
>> magnetic/orbital state, but of course not always. If the system feels
>> it is even with an external constrained potential not favorable, it
>> won't go into this state, (unless you specify a really large U value ?)
>>
>> And remember, LDA+U was made for real insulators, for "correlated
>> metals" only DMFT may help (wien2wannier + DMFT, see eg. unsupported
>> software).
>>
>>
>>
>> On 03/06/2013 02:55 PM, Hongbin Zhang wrote:
>>>
>>> Dear Prof. Blaha and wien users,
>>>
>>> Recently I am trying to do calculations on J=1/2 insulation iridates
>>> using
>>> LDA+U+SOC as implemented in WIEN2k. However, I found that it is very
>>> hard
>>> to converge to the desired insulating states with U smaller than 3 eV
>>> (J=0). Moreover, the ratio of spin and orbital moments is one if a large
>>> U, for instance, U=4 eV is used. This deviates also from what is
>>> expected
>>> that the ratio between spin and orbital moments should be 1/2.
>>>
>>> So my first questionsis , does any of you have ever done such
>>> calculations
>>> on J=1/2 iridates? I could not find any calculations done by wien2k
>>> in the
>>> literature. Is there any pitfalls that it is not doable?
>>>
>>> Since I could not converge it within normal self-consistent routines, I
>>> tried to make some density matrices up with desired spin/orbital moments
>>> and also occupation numbers. Then I do x orb -up/dn and afterwards self-
>>> consistent calculations with -orbc -so. After it converges, the orbital
>>> and spin moments are totally different from what is expected/designed.
>>> And also the density matrices in the case.scfdmup are quite different
>>> from
>>> my inputs.
>>>
>>> Here is my second question that how can one enforce the code to
>>> converge to a desired density matrix? Or one can only generate a rigid
>>> orbital potential and hope that the system will converge to the desired
>>> one?
>>>
>>> Any suggestion is welcome and appreciated!
>>>
>>> Regards,
>>>
>>> Hongbin
>>>
>>>
>>> _______________________________________________
>>> Wien mailing list
>>> Wien at zeus.theochem.tuwien.ac.at
>>> http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien
>>
>> --
>>
>>                                      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    WWW:
>> http://info.tuwien.ac.at/theochem/
>> --------------------------------------------------------------------------
>>
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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    WWW: 
http://info.tuwien.ac.at/theochem/
--------------------------------------------------------------------------