The calculation of bulk transport quantities (electrical and thermal resistivities - the part that is determined by the electron-phonon interaction) is possible using anaddb. Analogous quantities are obtained from the conducti post-processor, but due to electron-electron scattering, instead of electron-phonon.
A preliminary calculation of the derivatives of the wavefunctions with respect to k-vector must be carried out. After generating a GKK file (see topic_ElPhonInt), the Electron-Phonon Coupling (EPC) analysis is performed in anaddb, setting elphflag variable to 1. Most of the procedure is automatic, but can be lengthy if a large number of k-points is being used.
For the superconductivity calculations, The electron-phonon interaction is interpolated in reciprocal space, then integrated over the Fermi surface to give the Eliashberg function. Several quadrature methods are available. The default (telphint=1) is to use Gaussian weighting, with a width elphsmear. Another option is the improved tetrahedron [Bloechl1994a] (telphint=0). Finally (telphint=2), one can integrate a given set of electron bands, between ep_b_max and ep_b_min. The resulting integrated quantities are the Eliashberg function (in a file suffixed _A2F), and the EPC strength λ which is printed in the main output file.
The transport calculation is turned on by setting ifltransport to 1 in anaddb. The transport quantities depend on the Fermi velocity for each band, and the electronic band-dependence of the matrix elements must be preserved before integration, by setting ep_keepbands to 1. This increases the memory used, by the square of the number of bands crossing EF. The results are the transport Eliashberg function (in file _A2F_TR), the electrical resistivity (in file _RHO), and the thermal conductivity (in file _WTH).
It is also possible to consider the temperature dependence of the Fermi energy: cubic spline interpolation (ep_nspline) enables to linearly interpolate the transport arrays and reduce the memory usage. Besides setting the Fermi level with elph_fermie (in Hartree), it is also possible to specify the extra electrons per unit cell, (i.e., the doping concentration often expressed in cm-3) with ep_extrael.
Some details about the calculation of electron-phonon quantities in ABINIT and ANADDB can be found here.
Compulsory input variables:
... elphflag@anaddb [ELectron-PHonon FLAG]
Basic input variables:
... ep_keepbands@anaddb [Electron-Phonon KEEP dependence on electron BANDS]
... ifltransport@anaddb [IFLag for TRANSPORT]
... kptrlatt@anaddb [K PoinT Reciprocal LATTice]
... telphint@anaddb [Technique for ELectron-PHonon INTegration]
Useful input variables:
... a2fsmear@anaddb [Alpha2F SMEARing factor]
... elph_fermie@anaddb [ELectron-PHonon FERMI Energy]
... elphsmear@anaddb [ELectron-PHonon SMEARing factor]
... ep_b_max@anaddb [Electron Phonon integration Band MAXimum]
... ep_b_min@anaddb [Electron Phonon integration Band MINimum]
... ep_extrael@anaddb [Electron-Phonon EXTRA ELectrons]
... ep_nspline@anaddb [Electron Phonon Number for SPLINE interpolation]
... mustar@anaddb [MU STAR]
... prtfsurf@anaddb [PRinT the Fermi SURFace]
... prtvol@anaddb [PRinT VOLume]
Input variables for experts:
... band_gap@anaddb [BAND GAP]
... ep_nqpt@anaddb [Electron Phonon Number of Q PoinTs]
... kptrlatt_fine@anaddb [K PoinT Reciprocal LATTice for FINE grid]
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tests/v5/Input: t88.in t89.in t90.in t91.in t92.in t93.in t94.in t95.in t99.in
tests/v6/Input: t76.in t77.in t93.in t94.in t95.in
tests/v7/Input: t88.in
t93.in
t94.in
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