About
EPW is an open-source F90/MPI code for computing electron-phonon interactions and related materials properties using Density-Functional Perturbation Theory and Maximally Localized Wannier Functions. The name is derived from the words “Electron-phonon Wannier” which refer to the Wannier-Fourier interpolation method employed by the code. The name of the code is “EPW” (not “Electron-phonon Wannier”). The development of EPW is led by Sabyasachi Tiwari, Samuel Poncé, Emmanouil Kioupakis, Roxana Margine, and Feliciano Giustino.
The most recent reference technical manuscript is:
EPW is an independent code that is also distributed as part of the Quantum ESPRESSO materials simulation suite in collaboration with the Quantum ESPRESSO Foundation.
The code was written by Feliciano Giustino (EPW v1) while in the Cohen/Louie group at the University of California, Berkeley. Jesse Noffsinger (Berkeley) performed the integration with Quatum ESPRESSO (EPW v2). Brad Malone (Harvard) and Cheol-Hwan Park (Seoul National University) contributed with tests and benchmarks to EPW v2. Roxana Margine implemented the anisotropic Eliashberg theory while in the Giustino group at the University of Oxford (EPW v3). Carla Verdi developed the electron-phonon interpolation for polar materials including Froehlich correction while in the Giustino group at Oxford. Samuel Poncé made the code compatible with Quantum Espresso v5, optimized it, and developed an automatic test-farm for the code (EPW v4). He then implemented the electronic transport module while in the Giustino group at the University of Oxford (EPW v5). Hyungjun Lee coordinated code development in the Giustino group at the University of Texas at Austin (2019-2023). EPW v5 contains modules for indirect optical absoprtion (Emmanouil Kioupakis), and direct plus indirect absorption via quasidegenerate perturbation theory (Sabyasachi Tiwari). Sabyasachi Tiwari at UT Austin is the current project coordinator.
EPW is based on the method introduced in F. Giustino et al, Phys. Rev. B 76, 165108 (2007). An extended description of the most recent public release has been published in H. Lee al, npj Comput. Mater. 9, 156 (2023).
As of July 2024, the EPW Collaboration includes (in alphabetic order): Kyle Bushick, Bruno Cucco, Zhenbang Dai, Feliciano Giustino, Viet-Anh Ha, Emmanouil Kioupakis, Jon Lafuente-Bartolomé, Tae-Yun Kim, Chao Lian, Jae-Mo Lihm, Zhe Liu, Roxana Margine, Shashi Mishra, Hitoshi Mori, Samuel Poncé, Sabyasachi Tiwari, Aidan Thorn, Amanda Wang, Marios Zacharias, Xiao Zhang.
EPW is developed under git within the EPW GitLab portal.
As of July 2024, EPW consists of 94,039 lines of code (including comments).
Computing electron-phonon properties with EPW
EPW can be used to compute:
The total electron-phonon coupling strenght
The anisotropic Eliashberg spectral function
The transport spectral function
The anisotropic superconducting gap within the Eliashberg theory
The electron and phonon self-energies arising from the electron-phonon interaction
The phonon linewidths and lifetimes arising from the electron-phonon interaction
The electron linewidths and lifetimes arising from the electron-phonon interaction
The temperature-dependence of the carrier lifetimes
The spectral functions needed for the calculation of ARPES spectra
The temperature-dependent electron and hole mobility within the Boltzmann transport formalism
Magnetortransport coefficients such as the Hall mobility
Small and large polarons
Indirect phonon-assisted optical absorption
Temperature-dependent properties using the special displacement method
Direct plus indirect phonon-assisted absorption within quasidegenerate perturbation theory