Wannier90

Wannier90 is a software package designed to compute maximally localized Wannier functions (MLWFs) from first-principles electronic structure calculations. MLWFs provide a real-space, localized representation of electronic states that can exactly reproduce the Bloch bands within a chosen energy window. The code is intended to work with data produced by a variety of density functional theory (DFT) packages and to produce a tight-binding-like Hamiltonian in the Wannier basis, enabling efficient band structure interpolation and analysis.

Key features include a disentanglement procedure for handling entangled bands, a localization routine that minimizes the spatial spread of the Wannier functions, and tools to compute centers and spreads. Wannier90 can generate real-space Hamiltonian matrices, projections onto trial orbitals, and information necessary to reconstruct electronic properties in the Wannier representation. It supports interpolation of band structures, calculation of densities of states and Fermi surfaces, and the construction of model Hamiltonians for large-scale simulations or transport studies.

Typical workflow involves performing a DFT calculation with a compatible code, extracting the necessary Bloch-state information, and providing a seed file (seedname.win) to Wannier90 along with interface tools to prepare input data. Wannier90 then computes the unitary transformations that produce MLWFs and outputs the Wannier-related matrices and files needed to analyze or reuse the model in subsequent calculations.

Applications of Wannier90 span materials science and condensed matter physics, including accurate band interpolation, construction of tight-binding models, and exploration of electronic structure with reduced computational cost. It is widely used in combination with established first-principles codes and has become a standard tool for creating intuitive, localized representations of electronic states.