  BoltzTraP2 is a software package for calculating a smoothed Fourier
expression of periodic functions and the Onsager transport coefficients for
extended systems using the linearized Boltzmann transport equation. It uses
only the band and $k$-dependent quasi-particle energies, as well as the
intra-band optical matrix elements and scattering rates, as input. The code can
be used via a command-line interface and/or as a Python module. It is tested
and illustrated on a simple parabolic band example as well as silicon. The
positive Seebeck coefficient of lithium is reproduced in an example of going
beyond the constant relaxation time approximation.
