ifermi 0.1.4

📖📖 Online Documentation 📖📖

IFermi is a package for plotting Fermi surfaces and from ab initio calculation outputs. The main features include:

1. Plotting three-dimensional Fermi surfaces, with interactive plotting supported by mayavi, plotly and matplotlib.
2. Plotting slices of three-dimensional Fermi surfaces along a specified plane.

IFermi currently only supports VASP calculations but support for additional DFT packages will be added in the future.

Example

An example of the Fermi surface and a two-dimensional slice for MgB₂ is shown below:

Usage

The online documentation provides a full description of the available options. To summarise, three-dimensional Fermi surfaces can be plotted from a vasprun.xml file using:

ifermi

The two-dimensional slice of a Fermi slices along the plane specified by the miller indices (A B C) and distance d can be plotted from a vasprun.xml file using:

ifermi --slice A B C d

Python interface

Alternatively, IFermi can be controlled using the Python API. A full summary of the API is given in the API introduction page in the documentation.

The core classes in IFermi are:

• Inerpolator: to take a band structure on a uniform k-point mesh and interpolate it onto a denser mesh.
• FermiSurface: to store isosurfaces and reciprocal lattice information.
• FermiSurfacePlotter: to plot a Fermi surface from a FermiSurface object.

A minimal working example to plot the Fermi surface from a vasprun.xml file is:

from pymatgen.io.vasp.outputs import Vasprun
from ifermi.fermi_surface import FermiSurface
from ifermi.interpolator import Interpolator
from ifermi.plotter import FermiSurfacePlotter, show_plot, save_plot


vr = Vasprun("vasprun.xml")
bs = vr.get_band_structure()

# interpolate the energies to a finer k-point mesh
interpolator = Interpolator(bs)
dense_bs, kmesh = interpolator.interpolate_bands(interpolation_factor=10)

fs = FermiSurface.from_band_structure(dense_bs, kmesh, mu=0.0, wigner_seitz=True)
plotter = FermiSurfacePlotter(fs)
plot = plotter.get_plot(plot_type='plotly')

save_plot(plot, "fermi-surface.png")  # saves the plot to a file
show_plot(plot)  # displays an interactive plot

Note, if you're not running the example in a notebook then it must be proceeded by if __name__ == '__main__':.

Installation

IFermi can be installed with the command:

pip install ifermi

IFermi is currently compatible with Python 3.5+ and relies on a number of open-source python packages, specifically:

• pymatgen for parsing VASP calculation output.
• BoltzTrap2 for band structure interpolation.
• 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

Alex Ganose for developing/improving code and documentation. Sinead Griffin for suggesting the project.