Electron–phonon physics from first principles using the EPW code

Abstract

EPW is an open-source software for ab initio calculations of electron–phonon interactions and related materials properties. The code combines density functional perturbation theory and maximally localized Wannier functions to efficiently compute electron–phonon coupling matrix elements, and to perform predictive calculations of temperature-dependent properties and phonon-assisted quantum processes in bulk solids and low-dimensional materials. Here, we report on significant developments in the code since 2016, namely: a transport module for the calculation of charge carrier mobility under electric and magnetic fields using the Boltzmann transport equation; a superconductivity module for calculations of phonon-mediated superconductors using the anisotropic multi-band Eliashberg theory; an optics module for calculations of phonon-assisted indirect transitions; a module for the calculation of small and large polarons without supercells; and a module for calculating band structure renormalization and temperature-dependent optical spectra using the special displacement method. For each capability, we outline the methodology and implementation and provide example calculations.

Janus monolayer PXC (X = As/Sb) for photocatalytic water splitting with a negative Poisson's ratio

“…It's important to note that the deformation potential approach does not account for the electron–phonon interaction, which may result in an overestimation of carrier mobility to some extent. 51,54 However, according to previous literature reports, 55–57 the carrier mobility calculated by this deformation potential approach can still be used as a qualitative method to evaluate the trends and comparisons of mobility between different materials.…”

“…Hence, the light absorption of the material will be affected. 50 According to previous literature reports, 18,19,51 EPW and GW + BSE are both methods that can accurately be used to calculate the optical absorption properties. Here, we used the GW + BSE method to further calculate the optical properties of PXC monolayers, as shown in Fig.…”

Band Anisotropy Generates Axis-Dependent Conduction Polarity of Mg3Sb2 and Mg3Bi2

“…This is likely because that highly dispersive character of hole band in the Γ– A direction (Figure b) is not captured in constant relaxation time approximation. We suggest that a more detailed discussion will be possible by incorporating electron–phonon coupling in theoretical calculation . Another possible reason for the discrepancy is the uncertainty of the band gap estimation using density functional theory calculation.…”

“…We suggest that a more detailed discussion will be possible by incorporating electron−phonon coupling in theoretical calculation. 54 Another possible reason for the discrepancy is the uncertainty of the band gap estimation using density functional theory calculation. To examine the effect of band gap, we calculated band structure and transport coefficients of Mg 3 Bi 2 with varied lattice parameter a of 0.4626, 0.4646, 0.4666, 0.4686, and 0.4706 nm.…”

Dynamical Phonons Following Electron Relaxation Stages in Photoexcited Graphene

“…We implemented the nonequilibrium distributions in the calculation of electronic-structure properties and then calculated the renormalization of phonons with the PHonon , and EPW , codes in the adiabatic and nonadiabatic approximations (see the Supporting Information for more details). The resulting adiabatic phonon dispersions are shown in Figure .…”