Spin quantization axis

So, maybe a noob question. but.

In DOS calculations, Elk reports spin quantization axis , which is set by sqados variable.

The variable can be read from elk.in, which is not documented in the manual.

The questions:
- Does the axis even matter in a spin-unpolarized calculation? Would I get a different DOS with a non-z axis?
- Does it make a physical sense to set the axis in a direction other than the converged magnetization direction? I.e. if I set it perpendicular to the magnetization, would I get a symmetric ( up == down) DOS?
- In order to get a proper DOS from a non-collinear calculation, must I set sqados to the converged magnetization direction?

Thanks.

Hi Andrew,

In the case of collinear magnetism, the z spin quantisation axis (SQA) is the canonical choice because of the convention chosen for the Pauli matrices.

The utility of choosing a different SQA appears for non-collinear magnetism, or when the 'easy axis' is something other than z.

For example, if the moment in a particular muffin-tin is pointing in the x-direction, you can set the SQA to x and plot the partial DOS for that particular atom. This gives more physical information than that obained with a z SQA.

Regards,
Kay.

https://sourceforge.net/p/elk/discussion/897820/thread/2326d3fb48/