[Wien] Orientation of Atomic Spin Moments

[Chiung-Yuan Lin]

> 1) you calculate only S_z.
I just look at my last email, and it seems I didn't make myself clear
whether I am interested in the atomic spin of one magnetic atom or the
total spin from 2 such atoms. Here I clarify it: it's for one magnetic
atom.
When I run a regular spin-polarized calculation for a single magnetic
atom in the same environment (the magnetic atoms are on a surface, so
I can always leave only one), is the S_z from such calculation the
maximum S_z, which is the atomic spin S_a? If not, can I perform
several spin-orbit calculations with different magnetization
directions, find the S_z from the easy-axis case, and use it as S_a?

> 2) run ferromagnetic and antiferromagnetic calculations, and get J from
>    difference of total energies.
Does a regular spin-polarized calculation refer to the ferromagnetic case?
Is the energy difference related to J as 2JS^2 (FM: JS^2; AFM: -JS^2)?

Thank you,
Chiung-Yuan