[Pw_forum] About NON COLLINEAR magnetism

[Ralph Gebauer]

xianghjun wrote:

> An other related question is:
> Can PWNC deal with spin spirals?
> I have examined the input help file  "INPUT_NC",
> it seems  that the answer is "no".
> Am I right?
> Best regards,
> xianghjun
> 

Dear Xianghjun,

Unfortunately I'm not very familiar with the current
implementation of the noncollinear spin calculations
in pwscf. However, concerning your question about spin
spirals: Those can be quite easily calculated using a
"generalized Bloch theorem" in which a translation
by a lattice vector is also associated with a rotation
of the spin direction by a given angle. In this way,
spin spirals can be calculated without using a large
supercell, and spin spirals of arbitrary wave vector
can therefore be modelled using just the single unit
cell.

I'm quite sure that this generalized Bloch theorem is
no longer implemented in pwscf, but it is really not
difficult to program it (I had done so in a very old
version od the code).

If you are interested in details of this, and also in
how one can estimate the coupling constant J, you might
want to have a look at my PhD thesis which can be downloaded
from http://www.cecam.fr/activities/theses/theses.html .

Hope that helps,

Ralph


-----

Ralph Gebauer
The Abdus Salam International Centre for Theoretical Physics (ICTP)
Condensed Matter Section           Tel: (+39).040.2240.344
Strada Costiera 11                 Fax: (+39).040.224163
I-34014 Trieste (Italy)            e-mail: rgebauer at ictp.trieste.it