w2dynamics

Official Resources

• Homepage: https://github.com/w2dynamics/w2dynamics
• Documentation: https://github.com/w2dynamics/w2dynamics/wiki
• Source Repository: https://github.com/w2dynamics/w2dynamics
• License: GNU General Public License v3.0

Overview

w2dynamics is a continuous-time quantum Monte Carlo (CTQMC) impurity solver for multi-orbital systems within dynamical mean-field theory (DMFT). It provides efficient implementation of hybridization expansion and interaction expansion algorithms with MPI parallelization.

Scientific domain: Strongly correlated materials, DMFT calculations, many-body physics
Target user community: Researchers studying strongly correlated electron systems

Theoretical Methods

• Continuous-time quantum Monte Carlo (CTQMC)
• Hybridization expansion (CT-HYB)
• Interaction expansion (CT-INT)
• Dynamical Mean-Field Theory (DMFT) impurity solver
• Multi-orbital Anderson impurity model
• Worm sampling algorithms
• Maximum entropy analytical continuation
• Legendre polynomial expansion

Capabilities (CRITICAL)

• DMFT impurity solver for multi-orbital systems
• Single-site and cluster DMFT
• Self-energy calculations
• Green's functions in Matsubara and real frequencies
• Spectral functions via analytical continuation
• Density-density correlations
• Spin and orbital susceptibilities
• Magnetic and orbital order parameters
• General multi-orbital interactions
• Spin-orbit coupling
• Crystal field effects
• Interface to DFT codes for DFT+DMFT
• MPI parallelization

Sources: Official w2dynamics documentation, cited in 6/7 source lists

Inputs & Outputs

• Input formats:

  • HDF5-based input files
  • Configuration files (INI format)
  • Hybridization functions from DMFT loop

• Output data types:

  • HDF5 output with all observables
  • Self-energies (Matsubara frequencies)
  • Green's functions
  • Spectral functions
  • Occupation numbers and double occupancies
  • Correlation functions

Interfaces & Ecosystem

• DMFT frameworks:

  • solid_dmft - interface for DFT+DMFT
  • TRIQS compatibility (limited)
  • Custom DMFT loops possible

• DFT interfaces:

  • Works with Wannier functions from Wannier90
  • Interface to VASP, WIEN2k via solid_dmft

• Analysis tools:

  • Python scripts for post-processing
  • MaxEnt for analytical continuation
  • HDF5 format for data exchange

Limitations & Known Constraints

• CTQMC cost: Expensive; sign problem for some systems
• Analytical continuation: MaxEnt introduces uncertainties
• Multi-orbital complexity: Many parameters to converge
• Memory intensive: Large impurity problems demanding
• Statistical errors: Monte Carlo method; error bars on results
• Learning curve: DMFT and QMC concepts required
• Documentation: Good but assumes DMFT familiarity
• Platform: Linux/Unix; MPI required for large calculations

Performance Characteristics

• Efficiency: Highly optimized C++/Fortran core with efficient sampling updates.
• Parallelization: Massively parallel MPI implementation scaling to thousands of cores.
• Worm Sampling: Advanced worm algorithms improve ergodic sampling and convergence.

Comparison with Other Solvers

• vs iQIST: Both are similar CT-HYB/CT-INT solvers; iQIST offers more diverse interaction handling; w2dynamics has strong worm sampling support.
• vs TRIQS/cthyb: w2dynamics is a standalone solver; TRIQS/cthyb is part of a library. Both are state-of-the-art.
• vs ALPS/cthyb: w2dynamics offers superior performance and modern algorithms (worm sampling) compared to legacy ALPS.

Verification & Sources

Primary sources:

1. GitHub repository: https://github.com/w2dynamics/w2dynamics
2. Documentation: https://github.com/w2dynamics/w2dynamics/wiki
3. M. Wallerberger et al., Comput. Phys. Commun. 235, 388 (2019) - w2dynamics code
4. N. Parragh et al., Phys. Rev. B 86, 155158 (2012) - CT-HYB implementation

Secondary sources:

1. w2dynamics tutorials and examples
2. Published DFT+DMFT applications
3. solid_dmft documentation
4. Confirmed in 6/7 source lists (claude, g, gr, k, m, q)

Confidence: CONFIRMED - Appears in 6 of 7 independent source lists

Verification status: ✅ VERIFIED

• Official homepage: ACCESSIBLE (GitHub)
• Documentation: ACCESSIBLE
• Source code: OPEN (GitHub)
• Community support: Active (GitHub, developers)
• Academic citations: >100
• Active development: Regular updates