  elphbolt is a modern Fortran (2018 standard) code for efficiently solving the
coupled electron-phonon Boltzmann transport equations from first principles.
Using results from density functional and density functional perturbation
theory as inputs, it can calculate the effect of the non-equilibrium phonons on
the electronic transport (phonon drag) and non-equilibrium electrons on the
phononic transport (electron drag) in a fully self-consistent manner and
obeying the constraints mandated by thermodynamics. It can calculate the
lattice, charge, and thermoelectric transport coefficients for the temperature
gradient and electric fields, and the effect of the mutual electron-phonon drag
on these transport properties. The code fully exploits the symmetries of the
crystal and the transport-active window to allow the sampling of extremely fine
electron and phonon wave vector meshes required for accurately capturing the
drag phenomena. The coarray feature of modern Fortran, which offers native and
convenient support for parallelization, is utilized. The code is compact,
readable, well-documented, and extensible by design.
