# Phonon linewidth

### This page gives hints on how to compute the linewidth (or lifetime) of phonons, due to the electron-phonon interaction with the ABINIT package.

##### Copyright (C) 2016-2017 ABINIT group (MV)

Mentioned in topic_ElPhonInt, help_features#6.

### Table of content:

- 1. Introduction.
- 2. Related lesson(s) of the tutorial.
- 3. Related input variables.
- 4. Selected input files.

### 1. Introduction.

This topic concerns metals only.

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. The nqpath and qpath variables must be set, specifying a path in reciprocal space. anaddb generates files containing the phonon linewidths (suffixed _LWD) and frequencies ωqj (suffixed _BST) along qpath. One can calculate the nesting function n(q) = ∑kii' δ(εk,i) δ(εk+q,i') by setting prtnest to 1 (output to _NEST).

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### 2. Related lesson(s) of the tutorial.

- The lesson 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).
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### 3. Related input variables.

Compulsory input variables:

... elphflag@anaddb [ELectron-PHonon FLAG]

Basic input variables:

... kptrlatt@anaddb [K PoinT Reciprocal LATTice]
... nqpath@anaddb [Number of Q wavevectors defining a PATH]
... qpath@anaddb [Q wavevectors defining a PATH]
... telphint@anaddb [Technique for ELectron-PHonon INTegration]

Useful input variables:

... ep_int_gkk@anaddb [Electron-Phonon INTerpolation of GKK]
... ep_qptlist@anaddb [Electron Phonon Q PoinT LIST]
... ep_scalprod@anaddb [DO SCALar PRODuct for gkk matrix elements]
... ndivsm@anaddb [Number of DIVisions for the SMallest segment]
... prtnest@anaddb [PRinT the NESTing function]
... prtvol@anaddb [PRinT VOLume]

Input variables for experts:

... qgrid_type@anaddb [Q GRID TYPE]
... use_k_fine@anaddb [USE K-grid FINEr than the coarse k-grid]
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### 4. Selected input files.

WARNING : as of ABINITv8.6.x, the list of input files provided in the specific section of the topics Web pages is still to be reviewed/tuned. In some cases, it will be adequate, and in other cases, it might be incomplete, or perhaps even useless.
The user can find some related example input files in the ABINIT package in the directory /tests, or on the Web:

tests/tutorespfn/Input: teph_4.in teph_5.in

tests/v5/Input: t88.in t89.in t90.in t91.in t92.in t93.in t94.in t95.in t99.in

tests/v6/Input: t77.in t93.in t94.in t95.in

tests/v7/Input: t88.in t93.in t94.in
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