Electrons and Phonons from the materials project websiteΒΆ

This example shows how to dowload the electronic band structure and the DDB file using the mp identifier and use the AbiPy API to generate a matplotlib grid with electrons + phonons.

IMPORTANT: Electrons and Phonons have been obtained with different codes and different computational settings! Of course, one can always initialize ElectronBands and PhononBands from local netcdf files obtained with Abinit

../_images/sphx_glr_plot_eph_from_mp_001.png

Out:

Structure object does not have symmetry operations computed from Abinit.
Calling spglib to get symmetry operations.
/Users/gmatteo/git_repos/pymatgen/pymatgen/symmetry/bandstructure.py:63: UserWarning: The input structure does not match the expected standard primitive! The path can be incorrect. Use at your own risk.
  warnings.warn("The input structure does not match the expected standard primitive! "
Structure object does not have symmetry operations computed from Abinit.
Calling spglib to get symmetry operations.
Downloading DDB for mpid mp-149 (Si2) ...
Invoking anaddb to compute phonon bands...
Downloading DDB for mpid mp-66 (C2) ...
Invoking anaddb to compute phonon bands...
/Users/gmatteo/git_repos/abipy/abipy/examples/plot/plot_eph_from_mp.py:55: UserWarning: Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure.
  plt.show()

from abipy import abilab

# List of mp ids for Si, Diamond
mpids = ["mp-149", "mp-66"]

# Get list of AbiPy ebands from mpids
ebands_list = [abilab.ElectronBands.from_mpid(mpid) for mpid in mpids]

# Get list of DDB files from the MP website and run anaddb to get the phonon bands.
phbands_list = []
for i, mpid in enumerate(mpids):
    print("Downloading DDB for mpid %s (%s) ..." % (mpid, ebands_list[i].structure.formula))
    ddb = abilab.DdbFile.from_mpid(mpid)
    if ddb is None:
        raise RuntimeError("%d does not provide DDB" % mpid)
    print("Invoking anaddb to compute phonon bands...")
    phbst, _ = ddb.anaget_phbst_and_phdos_files(nqsmall=0)
    phbands_list.append(phbst.phbands)
    phbst.close()
    ddb.close()

# The figure has [len(mpids), 2] subplots
# The i-th row contains electrons and phonons for the i-th mp identifier.
nrows, ncols = len(mpids), 2
ax_mat, fig, plt = abilab.get_axarray_fig_plt(None, nrows=nrows, ncols=ncols,
                                              sharex=False, sharey=False, squeeze=False)

# Use the `ax` keyword argument to select the matplotlib Axes used to plot the object.
# In the band structure plot, we show the fundamental/direct gap as well as the possible
# phonon-absorption (-emission) processes allowed by energy-conservation.
# (This is a qualitative analysis of e-ph scattering, quasi-momentum and ph dispersion are not taken into account).
for i, (ebands, phbands) in enumerate(zip(ebands_list, phbands_list)):
    ebands.plot(ax=ax_mat[i, 0], with_gaps=True, ylims=(-5, 10), max_phfreq=phbands.maxfreq, show=False)
    phbands.plot(ax=ax_mat[i, 1], show=False)

    # Hide xlabel if not last row.
    if i != len(ebands_list) - 1:
        for ax in ax_mat[i]:
            ax.xaxis.label.set_visible(False)

plt.show()

Total running time of the script: ( 0 minutes 18.064 seconds)

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