Wannier90 as a community code: new features and applications (1907.09788v1)

Abstract: Wannier90 is an open-source computer program for calculating maximally-localised Wannier functions (MLWFs) from a set of Bloch states. It is interfaced to many widely used electronic-structure codes thanks to its independence from the basis sets representing these Bloch states. In the past few years the development of Wannier90 has transitioned to a community-driven model; this has resulted in a number of new developments that have been recently released in Wannier90 v3.0. In this article we describe these new functionalities, that include the implementation of new features for wannierisation and disentanglement (symmetry-adapted Wannier functions, selectively-localised Wannier functions, selected columns of the density matrix) and the ability to calculate new properties (shift currents and Berry-curvature dipole, and a new interface to many-body perturbation theory); performance improvements, including parallelisation of the core code; enhancements in functionality (support for spinor-valued Wannier functions, more accurate methods to interpolate quantities in the Brillouin zone); improved usability (improved plotting routines, integration with high-throughput automation frameworks), as well as the implementation of modern software engineering practices (unit testing, continuous integration, and automatic source-code documentation). These new features, capabilities, and code development model aim to further sustain and expand the community uptake and range of applicability, that nowadays spans complex and accurate dielectric, electronic, magnetic, optical, topological and transport properties of materials.

• The paper demonstrates that transitioning to a community-driven model has expanded Wannier90’s capabilities with symmetry-adapted functions and parallelized computations.
• The paper introduces methodological improvements including spinor support, refined Wannier interpolation, and the SCDM approach for more accurate electronic structure calculations.
• The paper highlights integrated post-processing modules and workflow automation that enable advanced studies of optical, transport, and nonlinear phenomena in materials.

An Overview of Wannier90 as a Community Code

The paper "Wannier90 as a community code: new features and applications" discusses the evolution of the Wannier90 program, detailing its transition to a community-driven model, and describes the various enhancements and functionalities introduced in version 3.0. Here, we provide an expert overview of the significant contributions and implications outlined in the paper.

New Developments and Features

Wannier90 is designed to calculate maximally-localized Wannier functions (MLWFs) from electronic structure calculations. The development of Wannier90 has shifted towards a community code model, leveraging contributions from a broader developer base. This shift has resulted in a multitude of new features, as detailed below:

1. Enhanced Wannierisation and Disentanglement:
   • The integration of symmetry-adapted Wannier functions (SAWFs) and selectively-localised Wannier functions (SLWFs) expands the capability of generating WFs that respect specific site symmetries.
   • Improvements in computational efficiency through parallelization, making use of MPI, permits the handling of larger systems with increased computational speed.
2. Expansion of Core Capabilities:
   • Spinor-valued WFs are now supported, which are crucial for systems with spin-orbit coupling.
   • An improved Wannier interpolation method that minimizes distances between orbitals enhances the accuracy and applicability of band structure calculations, particularly for systems calculated at the $\Gamma$ point.
3. Beyond Wannier90: New Post-Processing Features:
   • The introduction of modules for calculating shift currents, gyrotropic effects, and the spin Hall conductivity enables the paper of nonlinear optical and transport phenomena.
   • The inclusion of the SCDM method offers automatic generation of initial guesses for Wannierisation, bypassing the need for user-defined projections.
4. Incorporation of Modern Software Practices:
   • Enhanced code robustness and maintainability via continuous integration, unit testing, and comprehensive documentation using tools such as FORD for automatic documentation generation.
5. Community Engagement and Automation:
   • The incorporation of Wannier90 into the AiiDA infrastructure enables automated high-throughput computations and workflow management, facilitating reproducibility and efficient data management.

Implications and Future Prospects

The advancements in Wannier90 v3.0 have broadened its applicability across various areas of electronic structure theory, from improved band structure calculations to the predictive modeling of optical and transport properties. The community-driven development model and the integration with AiiDA suggest that Wannier90 will continue to evolve, potentially incorporating new features and improvements from a diverse set of contributors, thereby enhancing its capacity to handle increasingly complex material systems.

These developments will likely contribute to more comprehensive studies of emerging quantum materials, including topological insulators and Weyl semimetals, where Wannier functions have been shown to provide valuable insights into electronic properties.

The paper highlights how a well-coordinated community approach can significantly advance scientific software, demonstrating that open collaboration can lead to a sustainably maintained and feature-rich codebase that meets the evolving demands of the research community.

Overall, the transformation of Wannier90 into a community-supported platform exemplifies the potential of collaborative efforts in computational science, enabling the continuous growth and widespread application of this powerful tool in material science research.