Wannier90: A Tool for Obtaining Maximally-Localised Wannier Functions

TL;DR

Wannier90 is a versatile software tool that computes maximally-localized Wannier functions from electronic band structures, enabling efficient analysis and visualization of material properties across various computational methods.

Contribution

It introduces a basis-set independent, flexible implementation for calculating MLWFs from any electronic structure code, facilitating diverse applications in materials science.

Findings

Efficient computation of band-structure and density of states.

Supports visualization and post-processing of Wannier functions.

Applicable to a wide range of materials and electronic structure methods.

Abstract

We present Wannier90, a program for calculating maximally-localised Wannier functions (MLWF) from a set of Bloch energy bands that may or may not be attached to or mixed with other bands. The formalism works by minimising the total spread of the MLWF in real space. This done in the space of unitary matrices that describe rotations of the Bloch bands at each k-point. As a result, Wannier90 is independent of the basis set used in the underlying calculation to obtain the Bloch states. Therefore, it may be interfaced straightforwardly to any electronic structure code. The locality of MLWF can be exploited to compute band-structure, density of states and Fermi surfaces at modest computational cost. Furthermore, Wannier90 is able to output MLWF for visualisation and other post-processing purposes. Wannier functions are already used in a wide variety of applications. These include analysis of chemical bonding in real space; calculation of dielectric properties via the modern theory of polarisation; and as an accurate and minimal basis set in the construction of model Hamiltonians for large-scale systems, in linear-scaling quantum Monte Carlo calculations, and for efficient computation of material properties, such as the anomalous Hall coefficient. Wannier90 is freely available under the GNU General Public License from http://www.wannier.org/