[Wien] spin and orbital moment of vanadium

[Pavel Novak]

Dear Zhijian,

I have suggestion, which I am using sometimes, but it is a bit tricky.
Suppose you somehow know the final ground state of the system. You are 
then able to calculate how the electrons in this state are distributed 
i.e. you may calculate corresponding population matrix. From it
you calculate orbital potential using orb with sufficiently large U. This 
orbital potential will stabilize your selected state, so you proceed by
runsp_lapw -orbc
After it converges you may release orbital potential to see whether your 
selected state is stable.
Regards
Pavel


On Wed, 4 Nov 2009, Zhijian WU wrote:

> Dear Novak, Wu hua,and wein3k users,
> 
> Thanks a lot for your information. Concerning the valence state of V, we just tentatively assigned it as 2+, after careful checking, we found that it closes to 3+ (d^2). 
> 
> The procedure of our calculations is done as Pavel suggested. We first run GGA, then GGA+SOC. After that we run GGA+SOC+U. From GGA+SOC calculation, the orbital moment of V is very small, close to zero (about 0.0x). But even this small orbital moment still paralles with spin moment.After GGA+SOC+U calculation, initially, the orbital moment increases slightly with the increase of U, then after a certain U value, it has a sudden dramatic increase (the dramatic sudden increase has an explanation in a recent paper on MnV2O4 (102, 216405,2009, Phy. Rev. Lett.). During this process, the spin and orbital moments remain parallel. This is indeed weired because we have made many calculations on d orbitals of transition metals (including 3d, 4d and 5d transition metals) and such a strange thing never happened before. 
> 
> Any more suggestions?
> 
> Thank you very much!!
> 
> Regards,
> Zhijian 
> 
> ======= 2009-11-03 07:37:00 you wrote:=======
> 
> >Dear Zhijian WU,
> >
> >I recommend first to run the calculation without U (then L and S should 
> >be antiparallel) and only after it converged switch on the correlation. 
> >The reason is that LDA+U stabilizes the occupied states. If you switch it 
> >on from the beginning there is a danger that incorrect states will be 
> >stabilized.
> >
> >Regards
> >Pavel
> >
> >On Tue, 3 Nov 2009, Zhijian WU wrote:
> >
> >> Dear Wien2k users,
> >> 
> >> Recently, we calculated (spin-polarised calculations plus spin-orbit coupling and electron correlation U on vanadium) the spin and orbital moments of vanadium in a transition metal oxides. The valence state of vanadium can be assigned as +2, thus leaving the electronic configuration d^3 for vanadium. From our calculations, it is suprisingly found that the orbital moment paralells with spin moment, which violates the Hund's rule (which states that they should be antiparallel for less than half filled d orbitals). We doubt that something is wrong during our calculations, but can not figure out where or why.
> >> 
> >> Any hint or clue?
> >> 
> >> Thanks a lot for your inputs.
> >> 
> >> Regards,
> >> 
> >> Zhijian
> >> 
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> >> 
> >
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