[Wien] questions about ORB

[vahid ghanbarian]

Dear Dr. Novak,



Thank you very much for your attention. There are three questions.

1.        For the extra averaging of the LDA+U potential for system
without the centre of inversion, when LAPW1 must be complex, dose the
WIEN2k put Vmm, V-m-m ->(Vmm+V-m-m)/2 automatically or we must do this
work by hand? If by hand, how?

*2.        *Is the orbital field equal to zero when Vmm=V-m-m? If no,
why do we put Vmm, V-m-m ->(Vmm+V-m-m)/2?**

*3.        *When is the orbital field important?**

* *

Thanks

Vahid Ghanbarian



>Dear Vahid Ghanbarian,



>On Mon, 5 Dec 2005, vahid ghanbarian wrote:



>>* Dear WIEN2k users*

>>**

>>**

>>**

>>* In the ORB section of user's guide, the below statements were written:*

>>**

>>* If LDA+U is used in an unrestricted, general way, it introduces an orbital*

>>* field in the calculation. If the LDA+U orbital polarization is not needed,*

>>* it is sufficient to run real version of LAPW1, which then
automatically puts*

>>* the orbital field equal to zero. For systems without the center of
inversion*

>>* when LAPW1 must be complex, an extra averaging of LDA+U potential is*

>>* necessary.*

>>**

>>* I have some questions.*

>>**

>>* 1. Is this statement true? When we have a system with the centre of*

>>* inversion, all of the component of orbital dependent potential
will be real.*

>Orbital potential is a hermitean matrix, while the diagonal elements >are

>real, nondiagonal are in general complex.



>>**

>>* 2. Dose the real version of LAPW1 put the orbital field equal to zero in a*

>>* system with the centre of inversion that has only real component of orbital*

>>* dependent potential?*

>Yes, orbital field brings in Hamiltonian term linear in orbital momentum:

>B_orb.L, without spin-orbit coupling such term is incompatible with the

>space inversion symmetry.



>**

>>* 3. How can we do the extra averaging of the LDA+U potential for system*

>>* without the centre of inversion, when LAPW1 must be complex?*

>Orbital potential is a matrix in space of sherical harmonics Ylm.

>To average orbital potential you put Vmm, V-m-m -> (Vmm + V-m-m)/2.



>Regards

>Pavel Novak

>>**

>>**

>>**

>>* Best regards*

>>**

>>* Vahid Ghanbarian.*
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