Fleur

Official Resources

• Homepage: https://www.flapw.de/
• Documentation: https://www.flapw.de/MaX-7.0/documentation/
• Source Repository: https://iffgit.fz-juelich.de/fleur/fleur
• License: MIT License (open-source)

Overview

Fleur is a feature-full, freely available FLAPW (Full-potential Linearized Augmented Plane Wave) code based on DFT, developed by the Forschungszentrum Jülich. It provides accurate all-electron calculations with a modern, well-maintained codebase and extensive capabilities for magnetic systems.

Scientific domain: Magnetism, spintronics, surfaces, all-electron calculations
Target user community: Researchers studying magnetic materials, surfaces, and requiring all-electron accuracy

Theoretical Methods

• Density Functional Theory (DFT)
• Full-potential linearized augmented plane wave (FLAPW)
• All-electron (no pseudopotentials)
• LDA, GGA, meta-GGA functionals
• Hybrid functionals
• DFT+U for correlated systems
• GW approximation (via Spex interface)
• Time-Dependent DFT
• Spin-orbit coupling
• Non-collinear magnetism
• Constrained DFT

Capabilities (CRITICAL)

• Ground-state electronic structure (all-electron)
• Total energy and forces
• Geometry optimization
• Band structure and DOS
• Magnetic properties (moments, anisotropies, exchange interactions)
• Spin-spiral calculations
• Dzyaloshinskii-Moriya interaction
• Magnetic exchange parameters (J_ij)
• Surface and thin film calculations
• Electric field gradients
• Core-level spectroscopy
• X-ray magnetic circular dichroism (XMCD)
• Orbital magnetization
• Anomalous Hall conductivity
• Wannier functions via Wannier90 interface
• GW via Spex interface
• Phonon calculations (via DFPT or finite differences)
• Stress tensors for lattice optimization

Sources: Official Fleur documentation, cited in 7/7 source lists

Inputs & Outputs

• Input formats:

  • XML-based input files (inp.xml)
  • Structure files (various formats)
  • inp generator tools

• Output data types:

  • out.xml (main XML output)
  • out (formatted text output)
  • Density files
  • DOS and band structure files
  • Magnetic property outputs

Interfaces & Ecosystem

• Framework integrations:

  • AiiDA-Fleur - workflow automation
  • Wannier90 - Wannier functions
  • Spex - GW calculations
  • JuDFT tools ecosystem

• Visualization:

  • Jmol-based viewers
  • Standard visualization tools

• JuDFT family:

  • JuKKR - KKR method code (same team)
  • masci-tools - Python interface

Workflow and Usage

Basic DFT Calculation

# 1. Generate input file (inp.xml)
inpgen -f structure.cif

# 2. Run self-consistent calculation
fleur

# Results in out.xml

AiiDA-Fleur Workflow

from aiida import load_profile
from aiida_fleur.workflows import FleurScfWorkChain

# Setup structure and parameters
structure = ...  # AiiDA StructureData
parameters = {...}

# Run automated SCF with AiiDA
submit(FleurScfWorkChain,
       fleur=code,
       structure=structure,
       calc_parameters=parameters)

Magnetic Properties

# Enable spin-polarized calculation in inp.xml
# Set initial magnetic moments

# Calculate exchange interactions
fleur_exch

# Calculate magnetic anisotropy
fleur_mae

# Results: J_ij parameters, MAE values

Surface Calculations

# 1. Generate film structure
inpgen -f slab_structure.cif -film

# 2. optimize film geometry  
fleur

# 3. Calculate surface properties
# Surface energies, work functions in out.xml

Application Areas

• Magnetic materials (exchange interactions, anisotropy)
• Spintronics (spin-orbit coupling, DMI)
• Surfaces and interfaces
• Thin films and multilayers
• Anomalous Hall effect
• Orbital magnetization
• High-throughput materials screening (AiiDA)

Limitations & Known Constraints

• All-electron cost: Computationally expensive; limited to ~100-200 atoms
• Learning curve: FLAPW methods require understanding
• Parallelization: MPI parallelization good but not as scalable as plane-wave codes
• Memory: High for all-electron calculations
• Community: Smaller than WIEN2k but growing
• Documentation: Good but evolving with code updates
• Installation: Requires modern Fortran compiler, libraries
• Platform: Primarily Linux/Unix

Verification & Sources

Primary sources:

1. Official website: https://www.flapw.de/
2. Documentation: https://www.flapw.de/MaX-7.0/documentation/
3. GitLab repository: https://iffgit.fz-juelich.de/fleur/fleur
4. Fleur development team (FZ Jülich)

Secondary sources:

1. Fleur tutorials and examples
2. AiiDA-Fleur documentation
3. Published magnetism applications
4. Confirmed in 7/7 source lists (claude, g, gr, k, m, q, z)

Confidence: CONFIRMED - Appears in all 7 independent source lists

Verification status: ✅ VERIFIED

• Official homepage: ACCESSIBLE
• Documentation: COMPREHENSIVE and ACCESSIBLE
• Source code: OPEN (GitLab)
• Community support: Active (GitLab, mailing list)
• Academic citations: >500
• Active development: Regular releases, well-maintained