pymatgen.phonon.ir_spectra module

This module provides classes to handle the calculation of the IR spectra This implementation is adapted from Abipy https://github.com/abinit/abipy where it was originally done by Guido Petretto and Matteo Giantomassi

class IRDielectricTensor(oscillator_strength, ph_freqs_gamma, epsilon_infinity, structure)

Bases: MSONable

Class to handle the Ionic Dielectric Tensor The implementation is adapted from Abipy See the definitions Eq.(53-54) in :cite:`Gonze1997` PRB55, 10355 (1997).

Parameters:

• oscillator_strength – IR oscillator strengths as defined in Eq. 54 in :cite:`Gonze1997` PRB55, 10355 (1997).

• ph_freqs_gamma – Phonon frequencies at the Gamma point

• epsilon_infinity – electronic susceptibility as defined in Eq. 29.

• structure – A Structure object corresponding to the structure used for the calculation.

as_dict()

JSON-serializable dict representation of IRDielectricTensor.

classmethod from_dict(d)

Returns IRDielectricTensor from dict representation

get_ir_spectra(broad=5e-05, emin=0, emax=None, divs=500)

The IR spectra is obtained for the different directions

Parameters:

• broad – a list of broadenings or a single broadening for the phonon peaks

• emin (float) – minimum energy in which to obtain the spectra. Defaults to 0.

• emax (float) – maximum energy in which to obtain the spectra. Defaults to None.

• divs – number of frequency samples between emin and emax

Returns:

divs array with the frequencies at which the

dielectric tensor is calculated

dielectric_tensor: divsx3x3 numpy array with the dielectric tensor

for the range of frequencies

Return type:

frequencies

get_plotter(components=('xx',), reim='reim', broad=5e-05, emin=0, emax=None, divs=500, **kwargs)

Return an instance of the Spectrum plotter containing the different requested components

Parameters:

• components – A list with the components of the dielectric tensor to plot. Can be either two indexes or a string like ‘xx’ to plot the (0,0) component

• reim – If ‘re’ (im) is present in the string plots the real (imaginary) part of the dielectric tensor

• broad (float) – a list of broadenings or a single broadening for the phonon peaks. Defaults to 0.00005.

• emin (float) – minimum energy in which to obtain the spectra. Defaults to 0.

• emax (float) – maximum energy in which to obtain the spectra. Defaults to None.

• divs – number of frequency samples between emin and emax

• **kwargs – Passed to IRDielectricTensor.get_spectrum()

get_spectrum(component, reim, broad=5e-05, emin=0, emax=None, divs=500, label=None)

component: either two indexes or a string like ‘xx’ to plot the (0,0) component reim: only “re” or “im” broad: a list of broadenings or a single broadening for the phonon peaks

property max_phfreq

Maximum phonon frequency

property nph_freqs

Number of phonon frequencies

plot(components=('xx',), reim='reim', show_phonon_frequencies=True, xlim=None, ylim=None, **kwargs)

Helper function to generate the Spectrum plotter and directly plot the results

Parameters:

• components – A list with the components of the dielectric tensor to plot. Can be either two indexes or a string like ‘xx’ to plot the (0,0) component

• reim – If ‘re’ (im) is present in the string plots the real (imaginary) part of the dielectric tensor

• show_phonon_frequencies – plot a dot where the phonon frequencies are to help identify IR inactive modes

• xlim – x-limits of the plot. Defaults to None for automatic determination.

• ylim – y-limits of the plot. Defaults to None for automatic determination.

• kwargs – keyword arguments passed to the plotter

Keyword arguments controlling the display of the figure:

kwargs	Meaning
title	Title of the plot (Default: None).
show	True to show the figure (default: True).
savefig	“abc.png” or “abc.eps” to save the figure to a file.
size_kwargs	Dictionary with options passed to fig.set_size_inches e.g. size_kwargs=dict(w=3, h=4)
tight_layout	True to call fig.tight_layout (default: False)
ax_grid	True (False) to add (remove) grid from all axes in fig. Default: None i.e. fig is left unchanged.
ax_annotate	Add labels to subplots e.g. (a), (b). Default: False
fig_close	Close figure. Default: False.

write_json(filename)

Save a json file with this data