pymatgen.phonon.bandstructure module

class PhononBandStructure(qpoints, frequencies, lattice, nac_frequencies=None, eigendisplacements=None, nac_eigendisplacements=None, labels_dict=None, coords_are_cartesian=False, structure=None)[source]

Bases: monty.json.MSONable

This is the most generic phonon band structure data possible it’s defined by a list of qpoints + frequencies for each of them. Additional information may be given for frequencies at Gamma, where non-analytical contribution may be taken into account.

Parameters:
  • qpoints – list of qpoint as numpy arrays, in frac_coords of the given lattice by default
  • frequencies – list of phonon frequencies in THz as a numpy array with shape (3*len(structure), len(qpoints)). The First index of the array refers to the band and the second to the index of the qpoint.
  • lattice – The reciprocal lattice as a pymatgen Lattice object. Pymatgen uses the physics convention of reciprocal lattice vectors WITH a 2*pi coefficient.
  • nac_frequencies – Frequencies with non-analytical contributions at Gamma in THz. A list of tuples. The first element of each tuple should be a list defining the direction (not necessarily a versor, will be normalized internally). The second element containing the 3*len(structure) phonon frequencies with non-analytical correction for that direction.
  • eigendisplacements – the phonon eigendisplacements associated to the frequencies in cartesian coordinates. A numpy array of complex numbers with shape (3*len(structure), len(qpoints), len(structure), 3). he First index of the array refers to the band, the second to the index of the qpoint, the third to the atom in the structure and the fourth to the cartesian coordinates.
  • nac_eigendisplacements – the phonon eigendisplacements associated to the non-analytical frequencies in nac_frequencies in cartesian coordinates. A list of tuples. The first element of each tuple should be a list defining the direction. The second element containing a numpy array of complex numbers with shape (3*len(structure), len(structure), 3).
  • labels_dict – (dict) of {} this links a qpoint (in frac coords or cartesian coordinates depending on the coords) to a label.
  • coords_are_cartesian – Whether the qpoint coordinates are cartesian.
  • structure – The crystal structure (as a pymatgen Structure object) associated with the band structure. This is needed if we provide projections to the band structure
as_dict()[source]
asr_breaking(tol_eigendisplacements=1e-05)[source]

Returns the breaking of the acoustic sum rule for the three acoustic modes, if Gamma is present. None otherwise. If eigendisplacements are available they are used to determine the acoustic modes: selects the bands corresponding to the eigendisplacements that represent to a translation within tol_eigendisplacements. If these are not identified or eigendisplacements are missing the first 3 modes will be used (indices [0:3]).

classmethod from_dict(d)[source]
get_nac_eigendisplacements_along_dir(direction)[source]

Returns the nac_eigendisplacements for the given direction (not necessarily a versor). None if the direction is not present or nac_eigendisplacements has not been calculated.

Parameters:direction – the direction as a list of 3 elements
Returns:the eigendisplacements as a numpy array of complex numbers with shape (3*len(structure), len(structure), 3). None if not found.
get_nac_frequencies_along_dir(direction)[source]

Returns the nac_frequencies for the given direction (not necessarily a versor). None if the direction is not present or nac_frequencies has not been calculated.

Parameters:direction – the direction as a list of 3 elements
Returns:the frequencies as a numpy array o(3*len(structure), len(qpoints)). None if not found.
has_eigendisplacements

True if eigendisplacements are present.

has_imaginary_freq(tol=1e-05)[source]

True if imaginary frequencies are present in the BS.

has_nac

True if nac_frequencies are present.

min_freq()[source]

Returns the point where the minimum frequency is reached and its value

class PhononBandStructureSymmLine(qpoints, frequencies, lattice, has_nac=False, eigendisplacements=None, labels_dict=None, coords_are_cartesian=False, structure=None)[source]

Bases: pymatgen.phonon.bandstructure.PhononBandStructure

This object stores phonon band structures along selected (symmetry) lines in the Brillouin zone. We call the different symmetry lines (ex: Gamma to Z) “branches”.

Parameters:
  • qpoints – list of qpoints as numpy arrays, in frac_coords of the given lattice by default
  • frequencies – list of phonon frequencies in eV as a numpy array with shape (3*len(structure), len(qpoints))
  • lattice – The reciprocal lattice as a pymatgen Lattice object. Pymatgen uses the physics convention of reciprocal lattice vectors WITH a 2*pi coefficient
  • has_nac – specify if the band structure has been produced taking into account non-analytical corrections at Gamma. If True frequenciens at Gamma from diffent directions will be stored in naf. Default False.
  • eigendisplacements – the phonon eigendisplacements associated to the frequencies in cartesian coordinates. A numpy array of complex numbers with shape (3*len(structure), len(qpoints), len(structure), 3). he First index of the array refers to the band, the second to the index of the qpoint, the third to the atom in the structure and the fourth to the cartesian coordinates.
  • labels_dict – (dict) of {} this links a qpoint (in frac coords or cartesian coordinates depending on the coords) to a label.
  • coords_are_cartesian – Whether the qpoint coordinates are cartesian.
  • structure – The crystal structure (as a pymatgen Structure object) associated with the band structure. This is needed if we provide projections to the band structure
as_dict()[source]
classmethod from_dict(d)[source]
get_branch(index)[source]

Returns in what branch(es) is the qpoint. There can be several branches.

Parameters:index – the qpoint index
Returns:A list of dictionaries [{“name”,”start_index”,”end_index”,”index”}] indicating all branches in which the qpoint is. It takes into account the fact that one qpoint (e.g., Gamma) can be in several branches
get_equivalent_qpoints(index)[source]

Returns the list of qpoint indices equivalent (meaning they are the same frac coords) to the given one.

Parameters:index – the qpoint index
Returns:a list of equivalent indices

TODO: now it uses the label we might want to use coordinates instead (in case there was a mislabel)