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ElPhonInt

This page gives hints on how to compute the matrix elements of the electron-phonon interaction with the ABINIT package.

Introduction

The theory and details of the implementation are described in [Gonze2009] and [Gonze2016].

Basic calculations of electron-phonon interaction in ABINIT: one performs a normal ground state, then DFPT phonon calculations (using rfphon, with added keywords prepgkk and prtgkk, which saves the matrix elements to files suffixed GKK. The main change in this respect is that prtgkk now disables the use of symmetry in reducing q-points and perturbations. This avoids ambiguities in wave function phases due to band degeneracies. The resulting GKK files are merged using the mrggkk utility, and processed by anaddb.

With the implementation of phonons in PAW DFPT, the electron phonon coupling is also available in PAW, though this has not yet been tested extensively. The input variables for electron-phonon coupling in anaddb are described in [Gonze2009] and [Gonze2016].

Some details about the calculation of electron-phonon quantities in ABINIT and ANADDB can be found here.

Subsequently, the GKK file is used to compute many quantities, as explained in topic_PhononWidth, topic_TDepES and topic_ElPhonTransport.

A brand new ABINIT driver, focusing on the treatment of electron-phonon interaction is under development. Most of the input variables for experts, with optdriver==7 are related to this development, that is not yet operational as of v8.5.

compulsory:

basic:

useful:

  • dvdb_qcache_mb DVDB Q-CACHE size in Megabytes
  • eph_frohlichm Electron-PHonon: FROHLICH Model
  • eph_ngqpt_fine Electron-PHonon: Number of Grid Q-PoinTs in FINE grid.
  • get1den GET the first-order density from _1DEN file
  • getdvdb GET the DVDB from…
  • gkqwrite GKk for input Q grid to be WRITtEn to disk
  • irdddb Integer that governs the ReaDing of DDB file
  • irddvdb Integer that governs the ReaDing of DVDB file
  • use_nonscf_gkk USE NON-SCF calculation of GKK matrix elements (electron phonon)

expert:

  • ddb_shiftq Derivative DataBase: SHIFT of the Q-points
  • dvdb_add_lr DVDB ADD Long-Range part when interpolating DFPT potentials.
  • ep_prt_yambo Electron Phonon PRinTout YAMBO data
  • eph_ecutosc Electron-Phonon: Energy CUToff for OSCillator matrix elements
  • eph_extrael Electron-PHonon: EXTRA ELectrons
  • eph_fermie Electron-PHonon: FERMI Energy
  • eph_fsewin Electron-Phonon: Fermi Surface Energy WINdow
  • eph_fsmear Electron-PHonon: Fermi surface SMEARing
  • eph_intmeth Electron-Phonon: INTegration METHod
  • eph_mustar Electron-PHonon: MU STAR (electron-electron interaction strength)
  • eph_np_pqbks EPH Number of Processors for Perturbations, Q-points, Bands, K-points, Spin.
  • eph_stern Electron-PHonon: use STERNheimer approach to replace sum over empty states.
  • eph_transport Electron-PHonon: TRANSPORT flag
  • eph_use_ftinterp EPH FORCE Fourier Transform Interpolation of DFPT potentials.
  • getkerange_filepath KERANGE PATH
  • prtphdos PRinT the PHonon Density Of States
  • prtphsurf PRinT PHonon iso-SURFace
  • symgkq SYMmetrize the GKk matrix elements for each Q
  • symv1scf SYMmetrize V1 DFPT SCF potentials

Selected Input Files

v5:

v7:

Tutorials

  • The tutorial Response-Function 1 (RF1) presents the basics of DFPT calculations within ABINIT. The example given is the study of dynamical and dielectric properties of AlAs (an insulator): phonons at Gamma, dielectric constant, Born effective charges, LO-TO splitting, phonons in the whole Brillouin zone. The creation of the “Derivative Data Base” (DDB) is presented.
  • The tutorial on the electron-phonon interaction presents the use of the utility MRGKK and ANADDB to examine the electron-phonon interaction and the subsequent calculation of superconductivity temperature (for bulk systems).