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Hi
I am trying to model the bulk of UO2 with non-collinear 3k magnetism.

i have started by running a non-magnetic calculation - and taking the WAVECAR and CHGCAR
then I am not too sure I understand how to go about the next step

I need NONCOLLINEAR = .TRUE.
and then the MAGMOM tag has three digits per atom...but I am unsure how it should work
I have 8 oxygens and 4 uraniums in my unit cell
i have attempted
24*0 2 2 2 2 2 2 -2 -2 -2 -2 -2 -2
and 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 2 2 2 -2 -2 -2 -2 -2 -2

But I do not believe either give me the answer I am looking for as they appear to be very similar to the non-magnetic result.

I have also realised that the 3k magnetic structure is probably not well described by the above MAGMOM tag that I have used.

Any advice on how to correctly use the magmom tag for this 3k noncollinear magnetism would be much appreciated!

Thank you

Hi

The 3 integers of the MAGMOM tag correspond to the directions of the magnetic moment for a given atom

So if you want to study non magnetic UO2, the MAGMOM tag will be (0 0 0) for all atoms (U and O). If you want to study 1k AFM UO2, the MAGMOM tag will be (0 0 2) for two U atoms, then (0 0 -2) for the two other U atoms, and finally (0 0 0) for all oxygen atoms.

For the 3k structure, the magnetic moments of oxygen atoms are zero, so the corresponding MAGMOMs will be (0 0 0). For uranium atoms, however, magnetic moments are oriented along the <111> directions, so the MAGMOM tags wil be a bit more complicated. You can find them in the Table VI of this article: Phys Rev B 82, 035114 (2010)

Hope this helps

Thank you for your reply. I was wondering is it conventional to include brackets?
eg:
(2 2 2) (2 -2 -2) etc
or would it be more like:
2 2 2 2 -2 -2

Thanks again!

I have looked at the more complicated magnetisation for the 3k structure and carried out a calculation using the following:
MAGMOM: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 2 2 2 -2 -2 -2 2 -2 -2 -2 2
however I would expect the overall magnetisation to be 0 0 0 in the OSZICAR file but instead I see -2 -2 -2... perhaps I am misunderstanding