This package provides a user-friendly Python interface: abacusw90 to bridge ABACUS (Atomic-scale Simulation Package) with Wannier90. It automates the workflow of generating Maximally Localized Wannier Functions (MLWFs) and tight-binding models from ABACUS calculations.

Wannier90 is an open-source code that calculates maximally localized Wannier functions (MLWFs) from first-principles calculations. It is designed to:

• Generate maximally localized Wannier functions
• Calculate band structures and density of states
• Compute Berry phases and orbital magnetization
• Provide a basis for tight-binding models
• Support various first-principles calculation codes through interfaces

Wannier functions are particularly useful for:

• Electronic structure calculations
• Transport properties
• Spectroscopy calculations
• Model Hamiltonian construction

The abacusw90 package allows ABACUS to generate the necessary files for Wannier90, including:

• *.amn files: Overlap matrix between Bloch functions and Wannier functions
• *.mmn files: Overlap matrix between Bloch functions at neighboring k-points
• UNK* files: Bloch wavefunctions

• Various Basis Sets: Support for both plane wave (PW) and LCAO basis sets.
• Automated Workflow: Handles the core coupling pipeline (Steps 3-5 of the standard tutorial workflow).
• Input Generation: Automatically generates wannier90.win, INPUT, KPT, and STRU files.
• Method Support: Supports the recommended wannier_method = 2 for efficient overlap matrix calculation.
• Spin-Orbit Coupling: Full support for SOC calculations (nspin=4, lspinorb=1).

This directory contains three examples demonstrating different use cases of the ABACUS-Wannier90 interface:

• System: Diamond (C)
• Basis: LCAO (Linear Combination of Atomic Orbitals)
• Purpose: Demonstrates Wannier90 calculation using LCAO basis set
• Input Files:
  • INPUT-scf: ABACUS input file for SCF calculation
  • INPUT-nscf: ABACUS input file for NSCF calculation
  • KPT-scf: k-point sampling file for SCF calculation
  • KPT-nscf: k-point sampling file for NSCF calculation
  • STRU: Crystal structure file for diamond
  • diamond.win: Wannier90 input file
  • diamond.nnkp: Wannier90 preprocessing file

• System: Diamond (C)
• Basis: Plane wave (PW)
• Purpose: Demonstrates Wannier90 calculation using plane wave basis set
• Input Files: Similar to 01_lcao, but configured for plane wave basis

• System: Diamond (C)
• Basis: LCAO in plane wave mode
• Purpose: Demonstrates Wannier90 calculation using LCAO basis set in plane wave mode
• Input Files: Similar to 01_lcao, but configured for LCAO in plane wave mode

pip install .
# Or for development
pip install -e .

This interface automates the technical coupling steps between ABACUS and Wannier90. In the context of the standard tutorial workflow, it covers the following stages:

Here is an example of generating Wannier functions for Bi2Se3:

from abacusw90 import ABACUSWannier90
# 1. Initialize
# Assumes 'scf_dir' contains results from Step 1 (CHG, HR files)
job = ABACUSWannier90(work_dir="./Bi2Se3_wannier", scf_dir="./Bi2Se3_scf")
# 2. Define Structure
lattice = [[-2.069, -3.583614, 0.0], [2.069, -3.583614, 0.0], [0.0, 2.389075, 9.546667]]
atoms = [
    {"name": "Bi", "pos": [0.399, 0.399, 0.697]},
    {"name": "Bi", "pos": [0.601, 0.601, 0.303]},
    # ... (other atoms)
]
job.set_structure(lattice, atoms)
# 3. Configure Wannier90
# Parameters usually determined in Step 2 (Band structure analysis)
job.set_wannier_parameters(
    num_wann=30,
    num_bands=100,
    projections=["Bi : pz; px; py", "Se : pz; px; py"],
    dis_win_min=3.0,
    dis_win_max=18.0,
    dis_froz_min=3.0,
    dis_froz_max=14.8,
    mp_grid=[4, 4, 4],
    kpath=[
        {"start_label": "G", "start_pos": [0,0,0], "end_label": "Z", "end_pos": [0,0,0.5]}
    ]
)
# 4. Configure ABACUS
job.set_abacus_parameters(ecutwfc=100, nbands=100, lspinorb=1)
# 5. Run Automation (Covers Tutorial Steps 3, 4, 5)
job.run()

The run() method executes the following automated sequence:

1. Generate Inputs & Preprocess: Write wannier90.win and execute wannier90 -pp to generate .nnkp.
2. Prepare ABACUS: Parse .nnkp to generate ABACUS KPT, INPUT, and STRU files. Copy SCF charge densities.
3. Run ABACUS Interface: Execute ABACUS in NSCF mode with towannier90=1. This generates mmn, amn, eig files.
4. Run Wannier90: Execute wannier90.x to compute MLWFs and output wannier90_hr.dat.

• ABACUS: v3.0 or higher (with Wannier90 interface support).
• Wannier90: v3.0 or higher.
• Python: 3.8+

• The k-point grid in the ABACUS NSCF calculation must match the one in the Wannier90 input file
• Set wvfn_formatted = .true. in the Wannier90 input file to ensure compatibility with ABACUS output
• For LCAO calculations, ensure that the orbital basis set is appropriate for the Wannier functions you want to generate

• Files not found: Ensure ABACUS is generating *.amn, *.mmn, and UNK* files in the OUT.* directory
• Wannier90 cannot read ABACUS output: Check that wvfn_formatted = .true. is set in the Wannier90 input file
• Convergence issues: Ensure the SCF and NSCF calculations are properly converged

• Wannier90 website: http://www.wannier.org/
• Wannier90 paper: A. A. Mostofi et al., Comput. Phys. Commun. 185, 2309 (2014)
• ABACUS documentation: Refer to the ABACUS user manual for more details on input parameters