EPIq : an open-source software for the calculation of electron-phonon interaction related properties

TL;DR

EPIq is an open-source software that enables high-accuracy calculation of electron-phonon interaction properties from first principles, integrating with Quantum ESPRESSO and wannier90, and supporting various advanced features.

Contribution

EPIq introduces a versatile, open-source tool that calculates electron-phonon related properties efficiently and accurately, with customizable inputs and integration with anharmonic effects.

Findings

Accurate phonon dispersion calculations including non-adiabatic effects.

Superconducting properties, such as the band gap, can be computed.

Supports calculation of Raman spectra and carrier lifetimes.

Abstract

EPIq (Electron-Phonon wannier Interpolation over k and q-points) is an open-source software for the calculation of electron-phonon interaction related properties from first principles.Acting as a post-processing tool for a density-functional perturbation theory code ( Quantum ESPRESSO ) and wannier90, EPIq exploits the localization of the deformation potential in the Wannier function basis and the stationary properties of a force-constant functional with respect to the first-order perturbation of the electronic charge density to calculate many electron-phonon related properties with high accuracy and free from convergence issues related to Brillouin zone sampling. EPIq features includes: the adiabatic and non-adiabatic phonon dispersion, superconducting properties (including the superconducting band gap in the Migdal-Eliashberg formulation), double-resonant Raman spectra and lifetime of excited carriers. The possibility to customize most of its input makes EPIq a versatile and interoperable tool. Particularly relevant is the interaction with the Stochastic Self-Consistent Harmonic Approximation (SSCHA) allowing anharmonic effects to be included in the calculation of electron-properties. The scalability offered by the Wannier representation combined with a straightforward workflow and easy-to-read input and output files make EPIq accessible to the wide condensed matter and material science communities.