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Dear Vasp users,
For spin-spiral calculations, I know that I have to set LSPIRAL = .T., QSPIRAL = propagation vector, and LNONCOLLINEAR = .T.. My question is that after the self-consistent calculations, the resulting magnetization always lies in XY plane. For example, intially we set the MAGMOM = 4 4 4 or MAGMOM = 2 1 3, the results of total energy is the same and the magnetizations are all in the XY plane (z component is 0).
I've tested for many different cases such as bulk, surface, and even monolayers. Is there an input for rotation angle or somthing I miss ?

Hi,

I experienced the same. I guess the origin lies in
the full relaxation of the spin spiral calculations, i.e. relaxation of
the size of the local moment as well as the direction (cone angle).
Therefore, the reason why the system usually relaxes within the xy-plane (90degree) is most likely because its energetically more favorable than a smaller angle.

I would also highly appreciate the possibility to force the angle of the
spin spiral (between 90 and 0 degree). Probably realized by a magnetic field?
Is it possible in Vasp?

Best!