Generate 2D k-mesh

POSCAR is needed to to get the lattice information. the following command generates a k-mesh (-0.2 <= x <= 0.2 and -0.2 <= y <= 0.2) on the xy plan and around the \(\Gamma\) point with 21 points along each dimension.

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import mcu
mymcu = mcu.POSCAR()
mymcu.get_2D_kmesh(origin=[0,0,0], krange=[0.2,0.2], plane='xy', npoint=[21,21])

You should get the KPOINTS file generated. This is not done yet. Copy the k-mesh block in IBZKPT file to the KPOINTS file and do a simple math to figure out how many k-points in total. This new KPOINTS file should be ready for band structure calculation step.

Parameters

originlist

  • Default: [0,0,0] or \(\Gamma\) point

  • Fractional coordinates of the origin of the mesh

krangelist

  • Default: [0.1,0.1]

  • The first indicates -0.2 <= x <= 0.2, similarly for the second dimension.

planestr

  • Default: ‘xy’

  • Options: ‘xy’, ‘xz’, ‘yz’

npointlist

  • Default: [11,11]

  • Number of k-points along each dimension

Plot 2D band structure

2D band structure can be generated by following this procedure

  • Run a conventional SCF calculation to get WAVECAR

  • Generate KPOINTS file for a 2D k-mesh using mcu

  • Run band structure calculation using the new KPOINTS file

After finishing the calculation, you should be able to plot it simly by:

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import mcu
mymcu = mcu.VASP()
mymcu.plot_band2D()

You can run the following example in the /mcu/example/Graphene_2D directory. You should get:

_images/gra_band2D.png

All parameters and their defaults of plot_band function are given below. Most of the parameters are passed to matplotlib functions. So more information can be found in matplotlib docs.

Parameters

efermifloat

  • Default: fermi level from vasprun.xml or OUTCAR

  • User can shift the Fermi level to a value

spinint

  • Default: 0

  • If ISPIN = 1: spin = 0

  • If ISPIN = 2: spin = 0 (Up spin) or 1 (Down spin)

bandlist

  • Default: VBM and CBM

  • Which bands to plot

cmapstr

  • Default: ‘bwr’

  • Colormap used in style = 3. Other colormap type can be found here

savebool

  • Default: False

  • True to save to an image

figsizetuple or list

  • Default: De(6,6)

  • Size of image in inch

fignamestr

  • Default: ‘BAND2D’

  • Name of the image

xlimlist or tuple

  • Default: from k-mesh

  • Plotting range for 1st momentum (k). Unit \(Angstrom^{-1}\)

ylimlist or tuple

  • Default: from k-mesh

  • Plotting range for 2nd momentum (k). Unit \(Angstrom^{-1}\)

zlimlist or tuple

  • Default: from band values

  • Plotting range for energy (eV)

fontsizeint

  • Default: 18

  • Font size

dpiint

  • Default: 600

  • Resolution of the image

formatstr

  • Default: ‘png’

  • Extension of the image

Plot spin texture

Spin texture can be generated by following the same procedure as 2D band structure except that one should add the key word LSORBIT = .TRUE. for SOC in INCAR file. After finishing the calculation, you should be able to plot it simly by:

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import mcu
mymcu = mcu.VASP()
mymcu.plot_spin(band=2)

You can run the following example in the /mcu/example/MoS2_spintexture directory. You should get:

_images/spin_texture.png

All parameters and their defaults of plot_spin function are given below. Most of the parameters are passed to matplotlib functions. So more information can be found in matplotlib docs.

Parameters

styleint

  • Default: 1

  • Style = 1: the colormap for the third dimension is in the background

  • Style = 2: the colormap for the third dimension is in the arrows themselves

lmstr or list of str

  • Default: all the atoms and lm

  • Use can specify an orbital or a list of them, e.g. ‘Ni:s’ or [‘Ni:s’,’C:pz’]

bandint

  • Default: VBM

  • spin texture is plot for this band

cmapstr

  • Default: ‘bwr’

  • Colormap used in style = 3. Other colormap type can be found here

colorstr

  • Default: ‘k’

  • The color of the arrows used in the style = 1. No effect if style = 2

scaleint

  • Default: 15

  • Used to adjust the length of the arrow. The smaller the scale, the longer the arrows.

scale_unitsstr

  • Default: None

  • Used together with scale to play with the arrow’s length. Check here for more details

savebool

  • Default: False

  • True to save to an image

figsizetuple or list

  • Default: De(6,6)

  • Size of image in inch

fignamestr

  • Default: ‘spin_texture’

  • Name of the image

xlimlist or tuple

  • Default: from k-mesh

  • Plotting range for 1st momentum (k). Unit \(Angstrom^{-1}\)

ylimlist or tuple

  • Default: from k-mesh

  • Plotting range for 2nd momentum (k). Unit \(Angstrom^{-1}\)

fontsizeint

  • Default: 18

  • Font size

dpiint

  • Default: 600

  • Resolution of the image

formatstr

  • Default: ‘png’

  • Extension of the image