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I have been studying a magnetic material with SoC taken into consideration. The main aim was to obtain the band structure.

when I use spin_component = 1 in the bands.x input file, I get a bands.dat file containing the bands for the spinup configuration.

But on using spin_component = 2, it throws the following error.

 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     Error in routine punch_bands (1):
     incorrect spin_component
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

I found this discussion on the pw-Forum, in which it was stated that:

In the spin-orbit case starting with zero starting_magnetization on all atoms imposes time reversal symmetry. The magnetization is never calculated and kept zero (the internal variable domag is .FALSE.).

So is there a way to obtain the spin-polarized bandstructure in Quantum ESPRESSO whilst taking into consideration Spin-Orbit Coupling?

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    $\begingroup$ 'Spin-polarization' and SOC don't go along with each other. The wave function becomes a spinor when you include spin-orbit coupling. So there's no meaning of 'majority' or 'minority' carrier, since the spins can point in different directions. $\endgroup$
    – Xivi76
    Feb 5, 2021 at 21:35

1 Answer 1

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  • If you are considering SOC, which means the noncolinear calculations are performed. I assume that the eigenstate of the Kohn-Sham equation is labeled by $|atom, k, orbital, spin \rangle$. To obtain a spin-polarized band structure, you should do a fat band analysis with the consideration of the different spin components:

    • $\langle atom, k, orbital, spin|s_x \rangle$ (plus=left;minusright)
    • $\langle atom, k, orbital, spin|s_y \rangle$ (plus=front;minus=back)
    • $\langle atom, k, orbital, spin|s_z \rangle$ (plus=up;minus=down)

  • You may take a look at my answer for this post: Properties that can be deduced from Band structure and DOS

  • For your question, the key problem is to output band structure with projection to spin. The same function is realized with LORBIT=11 in VASP.

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