Fermi surface plotting tool from DFT output
Project description
IFermi is a Python (3.6+) library and set of command-line tools for the generation, analysis, and visualisation of Fermi surfaces and Fermi slices. The goal of the library is to provide full featured FermiSurface and FermiSlice objects which allow for easy manipulation and analysis. The main features include:
- Interpolation of electronic band structures onto dense k-point meshes.
- Extraction of Fermi surfaces and Fermi slices from electronic band structures.
- Projection of arbitrary properties on to Fermi surfaces and Fermi slices.
- Tools to calculate Fermi surface dimensionality, orientation, and averaged projections, including Fermi velocities.
- Interactive visualisation of Fermi surfaces and slices, with support for mayavi, plotly and matplotlib.
- Generation and visualisation of spin-texture.
IFermi currently only works with VASP calculations but support for additional DFT packages will be added in the future.
Quick start
The online documentation provides a full description of the available command-line options.
Analysis
Fermi surface properties, including dimensionality and orientation can be extracted from a vasprun.xml file using.
ifermi info
Fermi Surface Summary
=====================
# surfaces: 5
Area: 32.745 Å⁻²
Isosurfaces
~~~~~~~~~~~
Band Area [Å⁻²] Dimensionality Orientation
------ ------------ ---------------- -------------
6 1.944 2D (0, 0, 1)
7 4.370 1D (0, 0, 1)
7 2.961 2D (0, 0, 1)
8 3.549 1D (0, 0, 1)
8 3.549 1D (0, 0, 1)
Visualisation
Three-dimensional Fermi surfaces can be visualized from a vasprun.xml
file using:
ifermi plot
The two-dimensional slice of a Fermi surface along the plane specified by the miller
indices (j k l) and distance d can be plotted from a vasprun.xml
file using:
ifermi plot --slice j k l d
Python library
The ifermi
command line tools are build on the IFermi Python library. Here is an
example of how to load DFT calculation outputs, interpolate the energies onto a dense mesh,
generate a Fermi surface, calculate Fermi surface properties, and visualise the surface.
A more complete summary of the API is given in the API introduction page
and in the API Reference page in the documentation.
from pymatgen.io.vasp.outputs import Vasprun
from ifermi.surface import FermiSurface
from ifermi.interpolate import FourierInterpolator
from ifermi.plot import FermiSlicePlotter, FermiSurfacePlotter, save_plot, show_plot
# load VASP calculation outputs
vr = Vasprun("vasprun.xml")
bs = vr.get_band_structure()
# interpolate the energies onto a dense k-point mesh
interpolator = FourierInterpolator(bs)
dense_bs = interpolator.interpolate_bands()
# generate the Fermi surface and calculate the dimensionality
fs = FermiSurface.from_band_structure(
dense_bs, mu=0.0, wigner_seitz=True, calculate_dimensionality=True
)
# number of isosurfaces in the Fermi surface
fs.n_surfaces
# number of isosurfaces for each Spin channel
fs.n_surfaces_per_spin
# the total area of the Fermi surface
fs.area
# the area of each isosurface
fs.area_surfaces
# loop over all isosurfaces and check their properties
# the isosurfaces are given as a list for each spin channel
for spin, isosurfaces in fs.isosurfaces.items():
for isosurface in isosurfaces:
# the dimensionality (does the surface cross periodic boundaries)
isosurface.dimensionality
# what is the orientation
isosurface.orientation
# does the surface have face properties
isosurface.has_properties
# calculate the norms of the properties
isosurface.properties_norms
# calculate scalar projection of properties on to [0 0 1] vector
isosurface.scalar_projection((0, 0, 1))
# uniformly sample the surface faces to a consistent density
isosurface.sample_uniform(0.1)
# plot the Fermi surface
fs_plotter = FermiSurfacePlotter(fs)
plot = fs_plotter.get_plot()
# generate Fermi slice along the (0 0 1) plane going through the Γ-point.
fermi_slice = fs.get_fermi_slice((0, 0, 1))
# number of isolines in the slice
fermi_slice.n_lines
# do the lines have segment properties
fermi_slice.has_properties
# plot slice
slice_plotter = FermiSlicePlotter(fermi_slice)
plot = slice_plotter.get_plot()
save_plot(plot, "fermi-slice.png") # saves the plot to a file
show_plot(plot) # displays an interactive plot
Installation
IFermi can be installed with the command:
pip install ifermi
IFermi is currently compatible with Python 3.6+ and relies on a number of open-source python packages, specifically:
- pymatgen for parsing DFT calculation output.
- BoltzTrap2 for band structure interpolation.
- trimesh for manipulating isosurfaces.
- matplotlib, mayavi, and plotly for three-dimensional plotting.
What’s new?
Track changes to IFermi through the changelog.
Contributing
We greatly appreciate any contributions in the form of Pull Request. We maintain a list of all contributors here.
License
IFermi is made available under the MIT License.
Acknowledgements
Developed by Amy Searle and Alex Ganose. Sinead Griffin designed and led the project.
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