The elphbolt ab initio solver for the coupled electron-phonon Boltzmann transport equations

Abstract

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 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.

Mixed-Domain Charge Transport in the S–Se System from First-Principles

“…Analytical theories of these scattering phenomena for a plain parabolic band date back many decades, but developed only recently are the computational tools suitable for treating DFT band structures within nonprohibitive computing time, at least for simple structures. Many of these methods − rely on density-functional perturbation theory (DFPT), , some additionally on interpolation via Wannier functions, − to obtain electron–phonon scattering matrix elements, which are highly cumbersome for large, complex, low-symmetry systems such as S 1– x Se x at even a relatively coarse k -point mesh.…”

LinReTraCe: The Linear Response Transport Centre

“…While metallic systems suffer mostly from too coarse momentum grids, gapped systems tend to exhibit massive numerical instabilities. 17 Due to the additional Γ-smearing in our formalism, this problem is absent for reasonably large scattering rates (Γ ≥ 10 −6 eV) and reasonable band gaps (∆ < 10eV) at all temperatures when using Eq. ( 70).…”

“…Being agnostic to the input's origin, LinReTraCe can be used in a variety of settings, including electronic structures from tight-binding or Wannier projections [5], density functional theory (DFT) [6], many-body perturbation theory [7,8], dynamical mean-field theory (DMFT) [9,10], or approaches beyond [11,12]. Scattering amplitudes and many-body renormalizations can be phenomenological, extracted from electronic self-energies (obtained, e.g., from DMFT), or could incorporate results from electron-phonon codes [13][14][15][16][17][18][19]. In this release we include interfaces to the DFT codes WIEN2k [20,21] and VASP [22], the band interpolation tool of BoltzTraP2 [23,24], maximally localized Wannier functions of Wannier90 [25], as well as tools for general tight-binding systems.…”

Thermal conductivity reduction in highly-doped cubic SiC by phonon-defect and phonon-electron scattering

“…We also point out that electrons are taken to be in equilibrium when calculating ph-el scattering rates, which thus leads to the decoupled BTE. More rigorously, those interactions between non-equilibrium electrons and phonons should also be considered within the coupled el-ph BTEs [30]. Recent studies have found that it has significant effects on Seebeck coefficient and mobility in doped semiconductors [31].…”