EPW: Electron-phonon coupling, transport and superconducting properties using maximally localized Wannier functions

TL;DR

EPW is a software tool that uses maximally localized Wannier functions to accurately and efficiently compute electron-phonon interactions and related properties in solids, supporting advanced features like spin-orbit coupling and parallelization.

Contribution

The paper introduces EPW v4, a significantly optimized and feature-rich version of the software integrated with Quantum ESPRESSO for advanced electron-phonon property calculations.

Findings

Achieved nearly tenfold speedup over previous versions.

Supported new features like spin-orbit coupling and non-centrosymmetric symmetry.

Ensured stability and portability across major architectures.

Abstract

The EPW (Electron-Phonon coupling using Wannier functions) software is a Fortran90 code that uses density-functional perturbation theory and maximally localized Wannier functions for computing electron-phonon couplings and related properties in solids accurately and efficiently. The EPW v4 program can be used to compute electron and phonon self-energies, linewidths, electron-phonon scattering rates, electron-phonon coupling strengths, transport spectral functions, electronic velocities, resistivity, anisotropic superconducting gaps and spectral functions within the Migdal-Eliashberg theory. The code now supports spin-orbit coupling, time-reversal symmetry in non-centrosymmetric crystals, polar materials, and $\mathbf{k}$ and $\mathbf{q}$-point parallelization. Considerable effort was dedicated to optimization and parallelization, achieving almost a ten times speedup with respect to previous releases. A computer test farm was implemented to ensure stability and portability of the code on the most popular compilers and architectures. Since April 2016, version 4 of the EPW code is fully integrated in and distributed with the Quantum ESPRESSO package, and can be downloaded through QE-forge at http://qe-forge.org/gf/project/q-e.