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Tutorial solutions

Preliminaries

Welcome to wannier90! This is the tutorial solutions booklet for the examples in the wannier90 v3.1.0 tutorial (http://www.wannier.org/doc/tutorial.pdf). Info on the installation process and the theory of Maximally Localized Wannier Functions (MLWFs) is not reported here as they can be found elsewhere.1 The solutions in this booklet are for v3.1.0 only! The following (open-source) programs are required to reproduce the plots and figures in this booklet:

  • gnuplot is used to plot bandstructures. It is available for many operating systems and is often installed by default on Unix/Linux distributions. In particular, we used gnuplot 4.6 patchlevel 6.
    http://www.gnuplot.info

  • Grace is another plotting tool to visualise bandstructures.
    http://plasma-gate.weizmann.ac.il/Grace/

  • Vesta is the default 3D visualisation program 2 adopted in this booklet. It is used to visualise crystal structures, volumetric data (such as WFs and densities). Download is available for several OS here: http://jp-minerals.org/vesta/en/.

  • XCrySDen is also used to visualise crystal structures and Fermi surfaces in particular. It is available for Unix/Linux, Windows (using cygwin), and OSX. To correctly display files from wannier90, version 1.4 or later must be used.
    http://www.xcrysden.org

  • VMD may also be used to visualise crystal structures and 3D-fields. It can also read a great variety of input formats and it comes with handy postprocessing tools. http://www.ks.uiuc.edu/Research/vmd

Disclaimer: All the band structure interpolations have been carried out with ws_distance = .false., which is the default value for the version 2.1. However, in the newer wannier90 releases, from version 3.0 onwards, the default value of ws_distance has been changed to .true., as, to the best of our knowledge, the Wigner-Seitz interpolation scheme never lowers the quality of the interpolation and it is often superior to the default scheme.

About these tutorial solutions

This solution manual consists of 24 sections, each containing the solutions, in the form of plots, tables, and text, to the corresponding example in the wannier90 v3.1.0 tutorial! For each example, only the outline and key questions from the tutorial are reported here. All of the wannier90 input files have been provided. From example 5 onwards, input files for the pwscf interface (http://www.quantum-espresso.org) to wannier90 have also been provided. You will need a recent working version of the Quantum ESPRESSO package (v6.2 and above), to run these examples. In particular, you will need pw.x and pw2wannier90.x, as explained in the wannier90 v3.1.0 tutorial. Please visit http://www.quantum-espresso.org to download the package and follow the instruction on the website for installation. Further details on how to run the calculations for each example may be found in the corresponding section of the wannier90 v3.1.0 tutorial. There are interfaces to a number of other electronic structure codes including: ABINIT (http://www.abinit.org), fleur (http://www.flapw.de), OpenMX (http://www.openmx-square.org/), GPAW (https://wiki.fysik.dtu.dk/gpaw/), VASP (http://www.vasp.at), and Wien2K (http://www.wien2k.at).

All the tests were performed on an x86_64 octa-core Intel(R) Xeon(R) CPU E5620 @2.40GHz. Two packages intel-suite/2015.3.187 and mkl/2015.3.187 were used for the compilation of wannier90. We expect some of the numerical results to depend on the architecture, the compiler distribution, e.g. gcc vs gfortran, the version of the compiler and the libraries. However, general trends should not be affected by these parameters and, in principle, it should be safe to ignore the differences between different set-ups. If you find that your results are significantly different from the one given in this booklet, please report it to the wannier90 developers team by opening an issue on the GitHub repository or by writing an email to the forum at wannier@quantum-espresso.org (we strongly recommend the first option). Moreover, if you know how to solve the issue and you have a fix for it, you can open a pull-request on the GitHub repo.

Contact us

If you have any suggestions on how this solution manual may be improved and for any other issue, open an issue on the official repository of the wannier90 code on GitHub or send an email on the forum at wannier@quantum-espresso.org (we strongly recommend the former). For the forum note that you will need to be registered. Emails from non-registered users will be deleted automatically. You can register by following the links at http://www.wannier.org/forum.html.

  1. To install wannier90 you can follow the instructions in the readme file of the wannier90 distribution. For an introduction to the theory, you can look at the wannier90 User guide, the wannier90 Tutorial and references therein. ↩

  2. K. Momma and F. Izumi. Vesta 3 for three-dimensional visualization of crystal, volumetric and morphology data. J. Appl. Crystallogr, 44:1272–1276, 2011. ↩