[Wien] Questions about "-orbc" calculations

[Peter Blaha]

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
>
>
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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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Email: blaha at theochem.tuwien.ac.at    WWW: 
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