EPWpy.QE.band_util#

Classes

BandUtil(system, prefix[, scf_file, ...])

Utility class for handling band structure data from Quantum ESPRESSO (QE) outputs.
class EPWpy.QE.band_util.BandUtil(system, prefix, scf_file='scf', scf_fold='scf', nscf_file='nscf', nscf_fold='nscf', ph_file='ph', ph_fold='ph', bs_fold='bs', bs_file='bs', epw_fold='epw', epw_file='epw')[source]#

Bases: object

Utility class for handling band structure data from Quantum ESPRESSO (QE) outputs.

This class provides convenient access to file and directory information associated with band structure, phonon, and EPW calculations, allowing downstream tools to locate and process relevant outputs.

system#

Name of the system or material (used as the main working directory).

Type:

str

prefix#

Common prefix used in Quantum ESPRESSO input/output files.

Type:

str

scf_file#

Name of the self-consistent field (SCF) input/output file (default: 'scf').

Type:

str

scf_fold#

Folder containing SCF calculation results (default: 'scf').

Type:

str

nscf_file#

Name of the non-self-consistent field (NSCF) input/output file (default: 'nscf').

Type:

str

nscf_fold#

Folder containing NSCF calculation results (default: 'nscf').

Type:

str

ph_file#

Name of the phonon input/output file (default: 'ph').

Type:

str

ph_fold#

Folder containing phonon calculation results (default: 'ph').

Type:

str

bs_file#

Name of the band structure input/output file (default: 'bs').

Type:

str

bs_fold#

Folder containing band structure calculation results (default: 'bs').

Type:

str

epw_file#

Name of the EPW input/output file (default: 'epw').

Type:

str

epw_fold#

Folder containing EPW calculation results (default: 'epw').

Type:

str

Examples

>>> bands = BandUtil(system='si', prefix='si')
>>> print(bands.bs_fold)
'bs'
>>> print(bands.scf_file)
'scf'
get_band_EPW(file=None)[source]#

Retrieve the interpolated band structure from an EPW calculation.

This method reads the EPW-generated band.eig file and extracts eigenvalues and k-points using the bnd.extract_band_eig utility function.

Parameters:

file (str, optional) -- Path to the EPW band structure eigenvalue file. Defaults to {system}/{epw_fold}/band.eig.

Returns:

Band_EPW -- Extracted EPW band structure data with shape (nk, nband).

Return type:

object

Examples

>>> bu = BandUtil(system='si', prefix='si')
>>> bands_epw = bu.get_band_EPW()
>>> print(bands_epw.eigenvalues[:5])
[ -5.78, -5.77, -5.75, -5.70, -5.68 ]
get_band_QE(file=None)[source]#

Retrieve the band structure data from a Quantum ESPRESSO output file.

This method reads the QE band structure output (typically from bs.out) and extracts eigenvalues and k-points using the bnd.extract_band_scf utility function.

Parameters:

file (str, optional) -- Path to the QE bandstructure output file. If not provided, it defaults to {system}/{bs_fold}/{bs_file}.out.

Returns:

Band_QE -- Extracted band structure data with shape (nk, nband).

Return type:

object

Examples

>>> bu = BandUtil(system='si', prefix='si')
>>> bands = bu.get_band_QE()
>>> print(bands.eigenvalues.shape)
(50, 10)
get_eff_mass(grid, file=None, nmax=5)[source]#

Get the effective mass tensor using FT method nmax = nmax nk1 = grid[0] nk2 = grid[1] nk3 = grid[2]

if file is None:

file = f'{self.system}/{self.nscf_fold}/{self.nscf_file}.out'

band = self.get_band_QE(f'{file}') kx=[1,0,0] ky=[0,1,0] kz=[0,0,0]

h=np.linspace(0.0,1,nk1,endpoint=False) k=np.linspace(0.0,1,nk2,endpoint=False) l=np.linspace(0.0,1,nk3,endpoint=False)

kpoints = np.array(k_mesh(h,k,l,kx,ky,kz))

print(np.shape(band),np.shape(kpoints))

interp_func, coeffs, Gints = fourier_fit(band,kpoints[:,:3], nmax = nmax)

qe = QE_XML("si/bs/si.xml") # or your file name qe.summary() kpts = qe.get_kpoints() eigs = qe.get_eigenvalues() cell = qe.get_lattice() kpoints_crys = kpoints_2pi_alat_to_fractional(kpts, cell, 10.262000) band_dft = extract_band_scf('si/bs/bs.out')

band = []

for kpt in kpoints_crys:

band.append(interp_func(kpt))

band = np.array(band) for ib in range(len(band[0,0,:])):

plt.plot(band[:,0,ib],color = 'k') plt.plot(band_dft[:,ib],color = 'crimson')

bvecs = recoproc_lat_cart(cell) min_arg = np.argmin(band[:,0,4]) print(effective_mass_tensor(kpoints_crys[min_arg,:], coeffs, Gints, cell*bohr2m, band = 3))

print(np.shape(band))

get_phonon_EPW(file=None)[source]#

Retrieve the phonon dispersion data interpolated by EPW.

This method reads the phonon frequency file phband.freq generated by EPW, which contains interpolated phonon frequencies along a specified q-path.

Parameters:

file (str, optional) -- Path to the EPW phonon frequency file. Defaults to {system}/{epw_fold}/phband.freq.

Returns:

epw_ph_band -- Extracted EPW phonon band frequencies with shape (nq, nmode) in THz.

Return type:

ndarray

Examples

>>> bu = BandUtil(system='si', prefix='si')
>>> epw_ph = bu.get_phonon_EPW()
>>> print(epw_ph.shape)
(200, 6)
get_phonon_QE(file=None)[source]#

Retrieve the phonon dispersion data from Quantum ESPRESSO.

This method reads the phonon frequency data from the matdyn.freq file (typically produced by matdyn.x) and converts frequencies from meV to THz using a conversion factor of 0.124.

Parameters:

file (str, optional) -- Path to the phonon frequency file. Defaults to {system}/{ph_fold}/{prefix}.freq.

Returns:

ph_band -- Extracted phonon band frequencies with shape (nq, nmode), expressed in meV.

Return type:

ndarray

Notes

The conversion factor 0.124 converts from cm^-1 → meV

Examples

>>> bu = BandUtil(system='si', prefix='si')
>>> ph = bu.get_phonon_QE()
>>> print(ph.shape)
(120, 6)
plot_band_EPW(file=None, **kwargs)[source]#

Plot the interpolated electronic band structure obtained from EPW.

This method reads the EPW-interpolated bandstructure data (typically from band.eig), aligns the bands to the Fermi level, and visualizes the interpolated dispersion using the internal plotting utility.

Parameters:

  • file (str, optional) -- Path to the EPW bandstructure file. Defaults to {system}/{epw_fold}/band.eig.

  • **kwargs (dict, optional) -- Additional keyword arguments passed to the plotting function plb.plot_band_prod (e.g., color, linewidth, figsize). Supported keys include: - xlabel : str, label for x-axis (default: "Wavevector") - ylabel : str, label for y-axis (default: "Energy (eV)")

Notes

  • The band structure is read from EPW’s interpolation output file (band.eig), typically generated after Wannier interpolation.

  • The Fermi level is automatically extracted from the SCF output file ({system}/{scf_fold}/{scf_file}.out).

  • The energy axis is shifted such that the Fermi level corresponds to 0 eV.

Example

>>> bu = BandUtil(system='graphene', prefix='gr')
>>> bu.plot_band_EPW(color_c='red', linewidth=1.0, xlabel='k-path', ylabel='Energy (eV)')
plot_band_QE(file=None, **kwargs)[source]#

Plot the electronic band structure obtained from Quantum ESPRESSO.

This method reads the Quantum ESPRESSO bandstructure output file (typically bs.out), extracts the band data, aligns it with the Fermi level, and plots the band structure using the built-in plotting utilities.

Parameters:

  • file (str, optional) -- Path to the Quantum ESPRESSO bandstructure output file. Defaults to {system}/{bs_fold}/{bs_file}.out.

  • **kwargs (dict, optional) -- Additional keyword arguments passed to the plotting function plb.plot_band_prod (e.g., color, linewidth, figsize). Supported keys include: - xlabel : str, label for x-axis (default: "Wavevector") - ylabel : str, label for y-axis (default: "Energy (eV)")

Notes

  • The Fermi level is automatically extracted from the SCF output file ({system}/{scf_fold}/{scf_file}.out).

  • The energy axis is shifted such that the Fermi level is set to 0 eV.

Example

>>> bu = BandUtil(system='si', prefix='si')
>>> bu.plot_band_QE(color_c='blue', linewidth=1.2)
plot_phonon_EPW(file=None, **kwargs)[source]#

Plot the phonon dispersion interpolated using EPW.

This method reads the EPW-generated phonon dispersion file (typically phband.freq) and visualizes the interpolated phonon bandstructure.

Parameters:

  • file (str, optional) -- Path to the EPW phonon frequency file. Defaults to {system}/{epw_fold}/phband.freq.

  • **kwargs (dict, optional) -- Additional keyword arguments passed to the plotting function plb.plot_band_prod (e.g., color, linewidth, figsize). Supported keys include: - xlabel : str, label for x-axis (default: "Wavevector") - ylabel : str, label for y-axis (default: "Energy (meV)")

Notes

  • The phonon frequencies are obtained from EPW’s phband.freq output.

  • Frequencies are assumed to be in meV.

  • The zero energy reference is set at 0 meV.

Example

>>> bu = BandUtil(system='graphene', prefix='gr')
>>> bu.plot_phonon_EPW(color='red', linewidth=1.2)
plot_phonon_QE(file=None, **kwargs)[source]#

Plot the phonon dispersion obtained from Quantum ESPRESSO.

This method reads the phonon frequencies calculated by QE (typically from matdyn.freq or {prefix}.freq), converts them to meV, and visualizes the phonon bandstructure.

Parameters:

  • file (str, optional) -- Path to the QE phonon frequency file. Defaults to {system}/{ph_fold}/{prefix}.freq.

  • **kwargs (dict, optional) -- Additional keyword arguments passed to the plotting function plb.plot_band_prod (e.g., color, linewidth, figsize). Supported keys include: - xlabel : str, label for x-axis (default: "Wavevector") - ylabel : str, label for y-axis (default: "Energy (meV)")

Notes

  • The phonon frequencies are extracted from QE’s matdyn.freq output.

  • Frequencies are converted to meV using the factor 0.124.

  • The zero energy reference is set at 0 meV.

Example

>>> bu = BandUtil(system='graphene', prefix='gr')
>>> bu.plot_phonon_QE(color='blue', linewidth=1.2)