# Positron calculations

### This page gives hints on how to set parameters for a calculation with a positron in the system. with the ABINIT package.

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

Mentioned in help_features#9.

### Table of content:

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

### 1. Introduction.

The lifetime of positrons and their annihilation rate can be computed, using the self-consistent two-component DFT, including force and stress computation, LDA and GGA, norm-conserving as well as PAW [Wiktor2015]. Doppler broadening can also be computed. The details of of the way to perform such calculations is given in the description of the positron input variable, as well as in the lesson on electron-positron annihilation.

Examples can be found in [Wiktor2013],[Wiktor2014],[Wiktor2014a] and [Wiktor2014b].
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### 2. Related lesson(s) of the tutorial.

- The lesson on electron-positron annihilation
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  ### 3. Related input variables.

  Compulsory input variables:

  ... positron [POSITRON calculation]

  Basic input variables:

  ... ixcpositron [Integer for the eXchange-Correlation applied to the electron-POSITRON interaction]
  ... posdoppler [POSitron computation of DOPPLER broadening]
  ... posnstep [POSitron calculation: max. Number of STEPs for the two-component DFT]
  ... posocc [POSitron calculation: OCCupation number for the positron]
  ... postoldfe [POSitron calculation: TOLerance on the DiFference of total Energy]
  ... postoldff [POSitron calculation: TOLerance on the DiFference of Forces]
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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/v4/Input: t95.in t96.in

  tests/v5/Input: t07.in

  tests/v7/Input: t35.in
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  ### 5. References.

  [Wiktor2013] J. Wiktor, G. Jomard, M. Torrent and M. Bertolus, "Electronic structure investigation of energetics and positron lifetimes of fully relaxed monovacancies with various charge states in 3C-SiC and 6H-SiC", Phys. Rev. B 87, 235207 (2013).
  DOI: 10.1103/PhysRevB.87.235207.
  [Wiktor2014] J. Wiktor, X. Kerbiriou, G. Jomard, S. Esnouf, M.-F. Barthe and M. Bertolus, "Positron annihilation spectroscopy investigation of vacancy clusters in silicon carbide: Combining experiments and electronic structure calculations", Phys. Rev. B 89, 155203 (2014).
  [Wiktor2014a] J. Wiktor, M.-F. Barthe, G. Jomard, M. Torrent, M. Freyss and M. Bertolus, "Coupled experimental and DFT+U investigation of positron lifetimes in UO2", Phys. Rev. B 90, 184101 (2014).
  [Wiktor2014b] J. Wiktor, G. Jomard and M. Bertolus, "Electronic structure calculations of positron lifetimes in SiC: Self-consistent schemes and relaxation effect", Nucl. Instrum. Meth. 327, 63 (2014).
  DOI: 10.1016/j.nimb.2013.09.050.
  [Wiktor2015] J. Wiktor, G. Jomard and M. Torrent, "Two-component density functional theory within the projector augmented-wave approach: Accurate and self-consistent computations of positron lifetimes and momentum distributions", Phys. Rev. B 92, 125113 (2015).
  DOI: 10.1103/PhysRevB.92.125113.

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