[Wien] Magnetization axis, SOC, and rotation

[Peter Blaha]

I'm not completely sure either without looking into the code.

But from what I remember, the vector (x,y,z) is converted into theta and 
phi angles (printed in some scf or outputso file) and this is what is 
actually used for rotation.

Regards

On 04/06/2018 01:54 PM, Leandro Salemi wrote:
> Dear WIEN2K users and developers,
> 
> 
> I have a question regarding the magnetization direction in SOC calculations.
> 
> For a general magnetization axis, the Sz component is defined to be 
> along this axis. But then, along which direction are laying Sx and Sy 
> ( I know that their mean value is zero but I'm interested in matrix 
> elements for given bands).
> 
> 
> Let's take a tetragonal system and call 100 the x-axis, 010 the y-axis 
> and 001 the z-axis. If one sets the magnetization along the z-axis, then 
> the Sz component is the one along the 001, right ?
> 
> 
> But now, if I set the magnetization axis to be the crystallographic 
> x-axis, then the Sz component ( psi_up^2 - psi_dn^2 ) is along the 
> x-axis, i.e. the crystallographic basis is not the same as the basis for 
> the spin.
> 
> But then, what about the x/y axis in the spin-basis ? I would say that 
> in that case, the z-axis has been rotated along the y axis so that we have
> z -> x   ( Sz is along the crystallographic x axis)
> x -> -z ( Sx is along the crystallographic -z axis)
> 
> y -> y ( Sy is along the crystallographic y axis)
> 
> If this is correct, then what about a magnetization along the 110 
> crystallographic axis ?
> 
> Is it a rotation of 90° along an axis which is perpendicular to the 
> z-axis and to the 110 axis ?
> 
> 
> Thank you in advance for any answer or hint on this topic,
> 
> 
> Best regards,
> 
> 
> Leandro
> 
> 
> 
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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