### Non-collinear magnetism setup

To configure a Fleur calculation incorporating non-collinear magnetism, some parameters have to be set in the calculationSetup section and further parameters have to be set for each atomGroup in the atomGroups section. Templates with default parameters are generated by using the input generator with the -explicit or -noco command line options.

An example for the magnetic input elements in the calculation setup section is:

<magnetism jspins="1" l_noco="F" l_ss="F" lflip="F">
<qss>.0000000000 .0000000000 .0000000000</qss>
<mtNocoParams l_mperp="F" l_mtNocoPot="F" l_relaxSQA="F" mag_mixing_scheme="0" mix_RelaxWeightOffD="1.00000000" l_constrained="F" mix_constr="1.00000000"/>
<sourceFreeMag l_sourceFree="F" l_scaleMag="F" mag_scale="1.00000000"/>
</magnetism>


The following attributes can/have to be modified here:

Tag Attribute Description
magnetism jspins Number of spins to consider, i.e. jspins="1" for non-magnetic, and ="2" for magnetic calculations
l_noco This boolean switch activated non-collinear calculations
l_ss This boolean switch is used to activate spin-spiral calculations.
lfip Flip the magnetisation. See section below for details
qss In case of a spin-spiral calculation you have to give the q-vector of the spiral here
mtNocoParams In this tag flags controlling the treatment of magnetism in the MT-spheres can be set.
l_mperp Here the output of the magnetization perpendicular to the chosen axis can be activated.
l_mtNocoPot Switching this to "T" will allow a fully unconstrained calculation in which the MT spin-offdiagonal potential is calculated and use in the SCF. (Needs l_mperp="T")
l_relaxSQA Adjust the local spin-quantization axis in the sphere in each iteration to the direction of the local magnetic moment. Needed for some features like LDA+U in a l_mtNocoPot="t" calculation.
mag_mixing_scheme In case of l_relaxSQA="T" different preconditioners can be tried out to accelerate the convergence of the magnetic direction. Currently values of 1-3 are implemented
mix_RelaxWeightOffD Weight used to increase the local off-diagonal magnetisation in the mag_mixing_scheme not "0" cases. Should be >1 to have an effect.
l_constrained Perform a calculation in which an additional constraining field is used to fix the direction of the moments. Typical value "0.5"
mix_constr Mixing factor used to determine the constraining field self-consistently
sourceFreeMag Switches to use a source-free correction to the XC-B-Field. (Experimental)

In addition to these global switches there is the nocoParams tag in each atomGroup to control magnetic calculations.

<nocoParams alpha="Pi/2.0" beta="Pi/4.0"
l_constrained="F" l_mtNocoPot="F" l_relaxSQA="F"/>


The following attributes have to be set here:

Attribute Description
alpha The 1st angle that determines the magnetic structure. It is equal to $\varphi$ in spherical coordinates.
beta The 2nd angle that determines the magnetic structure. It is equal to $\vartheta$ (measured from the z axis) in spherical coordinates.
Please note, that in a l_relaxSQA="T" calculation, these are only used in constructing the starting charge as the correspong angles are determined from the local magnetic moment
l_constrained These switches overwrite the corresponding global switches (optional).
l_mtNocoPot These switches overwrite the corresponding global switches (optional).
l_relaxSQA These switches overwrite the corresponding global switches (optional).

### Manipulating the magnetism

If you set the lfip="T" switch in the magnetism tag, you can manipulate the magnetisation in the spheres. To do so you need to specify a modInitDen flag in the atomGroup tag. Please be careful about the workflow as you do not want to do this contineously.

<modInitDen flipSpinTheta="0.0" flipSpinPhi="0.0" flipSpinScale="F">

Attribute Description
flipSpinTheta Rotate the magnetisation by this angle around the local "y" axis. This is done first.
spinFlipPhi Rotate the magnetisation by this angle around local "z" axis. Done after "theta" rotation.
flipSpinScale If "T" flip the local spin.
beta The 2nd angle that determines the magnetic structure. It is equal to $\vartheta$ (measured from the z axis) in spherical coordinates.
magMom (Experimental)