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I have generate a figure illustrating spin texture of one band of a type of material. However I do not know the exact value of the color of background which means (Sz) value. The figure was plotted using python. The python code has utilized the SPINTEXTURE_2D_GAMMA_CENTER.dat file generated by [652] function of vaspkit.

enter image description here

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1 Answer 1

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About the Units

I believe you have generated your .dat file with VASP. It is most likely that the values you are finding in the .dat file are coming from the PROCAR file which contains the spd- and site projected wave function character of each orbital:

# of k-points:    5         # of bands:   26         # of ions:    3

k-point     1 :    0.00000000 0.00000000 0.00000000     weight = 0.06250000

band     1 # energy  -17.37867948 # occ.  1.00000000

ion      s     py     pz     px    dxy    dyz    dz2    dxz  x2-y2    tot  
    1  0.144  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.145
    2  0.291  0.000  0.006  0.000  0.000  0.000  0.000  0.000  0.000  0.298
    3  0.291  0.000  0.006  0.000  0.000  0.000  0.000  0.000  0.000  0.298
tot    0.727  0.000  0.013  0.000  0.000  0.000  0.000  0.000  0.000  0.740

which would look like the following when you consider ISPIN=2 and LNONCOLLINEAR=.TRUE:

ion      s     py     pz     px    dxy    dyz    dz2    dxz  x2-y2    tot  
    1  0.144  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.000  0.145
    2  0.291  0.000  0.006  0.000  0.000  0.000  0.000  0.000  0.000  0.298
    3  0.291  0.000  0.006  0.000  0.000  0.000  0.000  0.000  0.000  0.298
tot    0.727  0.000  0.013  0.000  0.000  0.000  0.000  0.000  0.000  0.740
    1 -0.011 -0.000 -0.000 -0.000 -0.000 -0.000 -0.000  0.000 -0.000 -0.011
    2 -0.023 -0.000 -0.000  0.000  0.000 -0.000 -0.000  0.000 -0.000 -0.023
    3 -0.023 -0.000 -0.000  0.000  0.000 -0.000 -0.000  0.000 -0.000 -0.023
tot   -0.057 -0.000 -0.001  0.000  0.000 -0.000 -0.000  0.000 -0.000 -0.058 
    1 -0.142 -0.000  0.000  0.000  0.000  0.000 -0.000 -0.000 -0.000 -0.142
    2 -0.286  0.000 -0.006 -0.000 -0.000  0.000 -0.000 -0.000  0.000 -0.293
    3 -0.286  0.000 -0.006 -0.000 -0.000  0.000 -0.000 -0.000  0.000 -0.293
tot   -0.715  0.000 -0.012 -0.000 -0.000  0.000 -0.000 -0.000  0.000 -0.727
    1 -0.024 -0.000  0.000 -0.000 -0.000  0.000 -0.000  0.000 -0.000 -0.024
    2 -0.048  0.000 -0.001  0.000  0.000  0.000 -0.000  0.000  0.000 -0.049
    3 -0.048  0.000 -0.001  0.000  0.000  0.000 -0.000  0.000  0.000 -0.049
tot   -0.119  0.000 -0.002  0.000  0.000  0.000 -0.000  0.000  0.000 -0.121

The additional set of projections are for the spin down channel and projected magnetizations. The first set is the total (absolute) magnetization, while the remaining three sets of entries correspond to the three directions $j=1,2,3$. Those projectd magnetizations are calculated for the wavefunction of the electronic state with spin-up and spin-down components (spinor) and Pauli matrices, the spinor is a two-component vector that describes the spin state of the electron, while Pauli matrices represent the spin operators in the x, y, and z directions, respectively. These matrices describe the spin orientation and provide a mathematical representation of the spin components.

Thus the total absolute magnetization is a dimensionless quantity and does not have a specific unit associated with it. It is often normalized to the number of atoms or unit cell volume in the material to obtain a normalized magnetization value, such as magnetization per unit cell or magnetization per atom. Then I would say that if the total magentization is absolute and dimensionless, its components in the x, y, and z directions, should also be dimensionless and without specific units.

How to understand the plot:

We basically have two colors each of which represents a spin-up (positive spin polarization) or spin-down (negative spin polarization). this is an idicator that the majority of spins in certain region are aligned in a particular direction (in/out) of plane. The arrows in spin-texture plots represent the direction and magnitude of the electron spin at each point in the material. The length of the arrows corresponds to the magnitude of the spin, while the direction indicates the spin orientation.

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