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 .
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Compulsory input variables:
... optdriver [OPTions for the DRIVER]
... prepgkk [PREPAre GKK calculation]
... prtgkk [PRinT the GKK matrix elements file]
Useful input variables:
... get1den [GET the first-order density from _1DEN file]
... gkqwrite@anaddb [GKk for input Q grid to be WRITtEn to disk]
... irdddb [Integer that governs the ReaDing of DDB file]
... use_nonscf_gkk [USE NON-SCF calculation of GKK matrix elements (electron phonon)]
Input variables for experts:
... ddb_ngqpt [Derivative DataBase: Number of Grid points for Q-PoinTs]
... ddb_shiftq [Derivative DataBase: SHIFT of the Q-points ]
... ep_prt_yambo@anaddb [Electron Phonon PRinTout YAMBO data]
... 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_ngqpt_fine [Electron-PHonon : Number of Grid Q-PoinTs in FINE grid.]
... eph_task [Electron-PHonon: Task]
... eph_transport [Electron-PHonon: TRANSPORT flag]
... getddb [GET the DDB from ...]
... prtphdos [PRinT the PHonon Density Of States]
... prtphsurf [PRinT PHonon iso-SURFace]
... symgkq@anaddb [SYMmetrize the GKk matrix elements for each Q]
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tests/v5/Input: t96.in t97.in t98.in
tests/v7/Input: t89.in
t90.in
t91.in
t92.in
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