# Wannier functions in ABINIT

### This page gives hints on how to perform Wannier functions calculation with the ABINIT package.

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

Mentioned in help_features#8.

### Table of content:

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

### 1. Introduction.

There are two ways to obtain Wannier functions with ABINIT:

- The first one is to use an internal implementation of Projected Local Orbital Wannier functions [Amadon2008], [Amadon2015] that can be activated with the input variable plowan_compute. The variables plowan_bandi and plowan_bandf specifies the Kohn Sham bands that are used to built Wannier functions, whereas variables plowan_natom,plowan_iatom,plowan_nbl, plowan_lcalc, and plowan_projcalc specify the atoms, angular momentum and projectors corresponding to the projected local Orbital Wannier functions.

  In order to do Wannier interpolation or analysis of hopping integrals, real space Wannier functions can be built using the variables plowan_realspace and plowan_nt as well as plowan_it. Real space Hamiltonian for analysis is given in latex file whose name ending is "wanniereigen" and the band structure is given in the output and log file.

- The second one is to use the external code wannier90 (www.wannier.org) that calculates Maximally Localized Wannier Functions (MLWF). After a ground state calculation the Wannier90 code will obtain the MLWFs requiring just two ingredients:
  - The overlaps between the cell periodic part of the Bloch states.
  - As a starting guess the projection of the Bloch states onto trial localized orbitals.

  What ABINIT do is to take the Bloch functions from a ground state calculation and compute these two ingredients. Then, Wannier90 is run. Wannier90 is included as a library and ABINIT and the process is automatic, so that in a single run you can do both the ground state calculation and the computation of MLWFs. The input variables prtwant, w90iniprj and w90prtunk are related to the use of the wannier90 librairy.

Go to the top

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

- The lesson on Wannier90 deals with the Wannier90 library to obtain Maximally Localized Wannier Functions.
Go to the top

### 3. Related input variables.

Compulsory input variables:

... plowan_bandf [Projected Local Orbital WANnier functions BAND Final]
... plowan_bandi [Projected Local Orbital WANnier functions BAND Initial]
... plowan_compute [Projected Local Orbital WANnier functions COMPUTATION]
... plowan_iatom [Projected Local Orbital WANnier functions, Index of ATOM]
... plowan_lcalc [Projected Local Orbital WANnier functions, L values to use for CALCulation]
... plowan_natom [Projected Local Orbital WANnier functions, Number of ATOMs]
... plowan_nbl [Projected Local Orbital WANnier functions, NumBer of L values]
... plowan_projcalc [Projected Local Orbital WANnier functions, PROJectors values to use for CALCulation]
... prtwant [PRinT WANT file]

Basic input variables:

... w90iniprj [Wannier90- INItial PROJections]
... w90prtunk [Wannier90- PRINT UNKp.s file]

Useful input variables:

... plowan_it [Projected Local Orbital WANnier functions, Index of Translation.]
... plowan_nt [Projected Local Orbital WANnier functions, Number of Translation on which the real space values of energy are computed]
... plowan_realspace [Projected Local Orbital WANnier functions, activate REAL SPACE calculation.]
Go to the top

### 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/wannier90/Input: t01.in t02.in t03.in t11.in t12.in t13.in

tests/v7/Input: t71.in t72.in
Go to the top

### 5. References.

[Amadon2008] B. Amadon, F. Lechermann, A. Georges, F. Jollet, T. O. Wehling and A. I. Liechtenstein, "Plane-wave based electronic structure calculations for correlated materials using dynamical mean-field theory and projected local orbitals", Phys. Rev. B 77, 205112 (2008).
DOI: 10.1103/PhysRevB.77.205112.
[Amadon2015] B. Amadon and A. Gerossier, "Comparative analysis of models for the α-γ phase transition in cerium: A DFT+DMFT study using Wannier orbitals", Phys. Rev. B 91, 161103 (2015).
DOI: 10.1103/PhysRevB.91.161103.

Go to the top