def _bands_from_force_constants(data: ForceConstants, q_distance: Quantity, insert_gamma: bool = True, frequencies_only: bool = False, **calc_modes_kwargs ) -> Tuple[Union[QpointPhononModes, QpointFrequencies], XTickLabels, SplitArgs]: structure = data.crystal.to_spglib_cell() bandpath = seekpath.get_explicit_k_path( structure, reference_distance=q_distance.to('1 / angstrom').magnitude) if insert_gamma: _insert_gamma(bandpath) x_tick_labels = _get_tick_labels(bandpath) split_args = {'indices': _get_break_points(bandpath)} print( "Computing phonon modes: {n_modes} modes across {n_qpts} q-points" .format(n_modes=(data.crystal.n_atoms * 3), n_qpts=len(bandpath["explicit_kpoints_rel"]))) qpts = bandpath["explicit_kpoints_rel"] if frequencies_only: modes = data.calculate_qpoint_frequencies(qpts, reduce_qpts=False, **calc_modes_kwargs) else: modes = data.calculate_qpoint_phonon_modes(qpts, reduce_qpts=False, **calc_modes_kwargs) return modes, x_tick_labels, split_args
def sample_sphere_dos(fc: ForceConstants, mod_q: Quantity, sampling: str = 'golden', npts: int = 1000, jitter: bool = False, energy_bins: Quantity = None, **calc_modes_args ) -> Spectrum1D: """Sample the phonon DOS, averaging over a sphere of constant |q| Parameters ---------- fc Force constant data for system mod_q radius of sphere from which vector q samples are taken (in units of inverse length; usually 1/angstrom). sampling Sphere-sampling scheme. (Case-insensitive) options are: - 'golden': Fibonnaci-like sampling that steps regularly along one spherical coordinate while making irrational steps in the other - 'sphere-projected-grid': Regular 2-D square mesh projected onto sphere. npts will be distributed as evenly as possible (i.e. using twice as many 'longitude' as 'lattitude' lines), rounding up if necessary. - 'spherical-polar-grid': Mesh over regular subdivisions in spherical polar coordinates. npts will be rounded up as necessary in the same scheme as for sphere-projected-grid. 'Latitude' lines are evenly-spaced in z - 'spherical-polar-improved': npts distributed as regularly as possible using spherical polar coordinates: 'latitude' lines are evenly-spaced in z and points are distributed among these rings to obtain most even spacing possible. - 'random-sphere': Points are distributed randomly in unit square and projected onto sphere. npts Number of samples. Note that some sampling methods have constraints on valid values and will round up as appropriate. jitter For non-random sampling schemes, apply an additional random displacement to each point. energy_bins Preferred energy bin edges. If not provided, will setup 1000 bins (1001 bin edges) from 0 to 1.05 * [max energy] **calc_modes_args other keyword arguments (e.g. 'use_c') will be passed to ForceConstants.calculate_qpoint_phonon_modes() Returns ------- Spectrum1D """ qpts_cart = _get_qpts_sphere(npts, sampling=sampling, jitter=jitter ) * mod_q qpts_frac = _qpts_cart_to_frac(qpts_cart, fc.crystal) phonons = fc.calculate_qpoint_frequencies(qpts_frac, **calc_modes_args ) # type: QpointFrequencies if energy_bins is None: energy_bins = _get_default_bins(phonons) return phonons.calculate_dos(energy_bins)