Example of finding the bandgap

The ElectronicBandStructure is used to handle the information related to the electronic band structure.

General Format

import pyprocar
pyprocar.io.Parser(code="vasp", dir=data_dir)

Downloading example

 data_dir = pyprocar.download_example(save_dir='',
                             material='Fe',
                             code='vasp',
                             spin_calc_type='non-spin-polarized',
                             calc_type='bands')

# sphinx_gallery_thumbnail_number = 1

import pyvista as pv
# You do not need this. This is to ensure an image is rendered off screen when generating exmaple gallery.
pv.OFF_SCREEN = True

importing pyprocar and specify the local data_dir

import os
import numpy as np
import pyprocar

data_dir = f"{pyprocar.utils.ROOT}{os.sep}data{os.sep}examples{os.sep}Fe{os.sep}vasp{os.sep}non-spin-polarized{os.sep}fermi"

Initialize the parser object and get the ElectronicBandStructure

parser=pyprocar.io.Parser(code="vasp",dir=data_dir)
ebs=parser.ebs
e_fermi = parser.ebs.efermi
structure = parser.structure
# Apply symmetry to get a full kmesh
if structure.rotations is not None:
    ebs.ibz2fbz(structure.rotations)

You can print the object to see some information about the Band Structure

print(ebs)

Enectronic Band Structure
------------------------
Total number of kpoints  = 3375
Total number of bands    = 8
Total number of atoms    = 1
Total number of orbitals = 9

Let’s plot the kpoints

p=pv.Plotter()
p.add_mesh(ebs.kpoints, color='blue', render_points_as_spheres=True)
p.show()

Other properties

Bands

kpoints=pv.PolyData(ebs.kpoints)
kpoints['band_0']=ebs.bands[:,0,0]

p=pv.Plotter()
p.add_mesh(kpoints, color='blue', scalars='band_0', render_points_as_spheres=True, point_size=10)
p.show()

Projections

print(ebs.projected.shape)
kpoints['band_0-atom_0-orbital_5-spin-0']=ebs.projected[:,0,0,0,4,0]

p=pv.Plotter()
p.add_mesh(kpoints, color='blue', scalars='band_0-atom_0-orbital_5-spin-0', render_points_as_spheres=True, point_size=10)
p.show()

(3375, 8, 1, 1, 9, 1)

Gradients

print(ebs.bands_gradient.shape)
kpoints['band_0-gradients']=ebs.bands_gradient[:,:,0,0]

# Use the Glyph filter to generate arrows for the vectors
arrows = kpoints.glyph(orient='band_0-gradients', scale=False, factor=0.08)
p=pv.Plotter()
p.add_mesh(arrows,scalar_bar_args={'title':'band_0-band_velocity'})
p.show()

Traceback (most recent call last):
  File "Z:\Research Projects\pyprocar\examples\05-other\plot_ebs.py", line 99, in <module>
    arrows = kpoints.glyph(orient='band_0-gradients', scale=False, factor=0.08)
  File "Z:\Anaconda\envs\pyprocar_6.1.10\lib\site-packages\pyvista\core\filters\data_set.py", line 2315, in glyph
    dataset.set_active_vectors(orient, preference=prefer)
  File "Z:\Anaconda\envs\pyprocar_6.1.10\lib\site-packages\pyvista\core\dataset.py", line 692, in set_active_vectors
    raise ValueError(
ValueError: Data field (band_0-gradients) with type (FieldAssociation.POINT) could not be set as the active vectors

Band/Fermi velocities

print(ebs.fermi_velocity.shape)
kpoints['band_0-band_velocity']=ebs.fermi_velocity[:,:,0,0]
kpoints['band_0-band_speed']=ebs.fermi_speed[:,0,0]

arrows = kpoints.glyph(orient='band_0-band_velocity', scale=False, factor=0.08)
p=pv.Plotter()
p.add_mesh(kpoints, scalars='band_0-band_speed', render_points_as_spheres=True, point_size=0.1,show_scalar_bar=False)
p.add_mesh(arrows,scalar_bar_args={'title':'band_0-band_velocity'})
p.show()

Effective mass

print(ebs.harmonic_average_effective_mass.shape)
kpoints['band_0-harmonic_average_effective_mass']=ebs.harmonic_average_effective_mass[:,0,0]

p=pv.Plotter()
p.add_mesh(kpoints, scalars='band_0-harmonic_average_effective_mass', render_points_as_spheres=True, point_size=10)
p.show()