transport module¶

This module, transport.py contains the setup and checks necessary to execute the calculation of the transport coefficients. It also execute those routines.

Contains routines to set up the calculation of the charge carrier transport coefficients.

class transport.Transport(bs)¶

Bases: object

Involves all transport related routines.

Parameters

bsobject: A Band() object.
latticeobject: A Lattice() object.
paramobject: A Param() object.

calc_carrier_concentration(self, temperature, chempot, dos=None, dos_energies=None, band_decomp=False, defect_ionization=False)¶

Returns the charge carrier concentration.

Parameters

temperaturefloat: The temperature in K.
chempotfloat: The chemical potential in eV.
dosndarray, optional: Dimension: (N,M)

Contains the band decomposed density of states for each band N and energy M. If not supplied, set to the dos_partial parameter of the current Bandstructure() object.
dos_energiesndarray, optional: Dimension: (M)

The energies in eV where the density of states are sampled.
band_decompboolean: Return a band decomposed carrier concentration or not.
defect_ionizationboolean: Selects if defect ionization compensation should be included. The donor_number, donor_energy, donor_degen_fact, acceptor_number, acceptor_energy and acceptor_degen_fact need to be set in the general configuration file.

Returns

n_typendarray: Dimension: (N)

Contains the n-type carrier concentration for each band index N in units of $10^{21} \mathrm{cm}^{-3}$ .
p_typendarray: Dimension: (N)

Contains the p-type carrier concentration for each band index N in units of $10^{21} \mathrm{cm}^{-3}$ .

calc_transport_tensors(self, bs=None, temperatures=None, chempots=None, method=None)¶

Selects which method to use when calculating the transport coefficients.

Parameters

bsA Band() object containing the band structure.
temperaturesndarray, optional: Dimension: (N)

Contains N different temperatures in K. If not supplied the temperature from the active Transport() object is used.
chempotsndarray, optional: Dimension: (M)

Contains M different chemical potentials in eV. If not supplied the chempot from the active Transport() object is used.
method{“closed”, “numeric”, “numerick”}: If method is not supplied is defaults to “numeric” unless bandstructure data is read numerically or generated (all cases where the closed Fermi Dirac integrals cannot be used) when it defaults to “numerick”.

“closed” evaluates the closed Fermi integrals where only

one scattering mechanism is possible per band. Only valid

for systems where one can strictly rely on a parametrized

parabolic bandstructure based on effective mass models.

Parameters (e.g. effective masses for each band) are set

in the bandstructure configuration file.

The driver routine is lbtecoeff.parabolic_closed()

“numeric” similar to “closed, but evaluates the Fermi

integrals in an open form (e.g. it is possible to

concatenate the scattering mechanisms, which is not

possible for the closed Fermi integrals).

The driver routine is lbtecoeff.parabolic_numeric()

“numerick” evaluates the transport integrals more generally

as an integral over the k-points. It is less restrictive

than the two other options, but also more prone to

convergence issues etc. However, for bandstructures

read from datafiles, this is the only option.

The driver routine is lbtecoeff.numerick()

Returns

sigma, seebeck, lorenzndarray, ndarray, ndarray: Dimension: (N,M,3,3), (N,M,3,3), (N,M,3,3)

Returns the electrical condcutivity, Seebeck coefficient and Lorenz tensor for N temperature and M chemical potential steps in units of $\\mathrm{S}/\\mathrm{m}$ , $\\mu \\mathrm{V}/\\mathrm{K}$ , $\\mathrm{V^2}/\\mathrm{K^2}$ . These are stored in the current Transport() object.