Official Resources
- Homepage: https://github.com/pfloos/QuACK
- Documentation: https://github.com/pfloos/QuACK/wiki
- Source Repository: https://github.com/pfloos/QuACK
- License: GNU General Public License v3.0
Overview
QUACK (Quantum Chemistry in ACKnowledgement) is an open-source software for emerging quantum electronic structure methods. It specializes in Green's function methods including GW approximation and Bethe-Salpeter equation (BSE) for molecular systems, along with coupled cluster and other advanced correlation methods.
Scientific domain: Many-body perturbation theory, GW, BSE, coupled cluster for molecules
Target user community: Researchers developing and applying GW/BSE methods to molecular systems
Theoretical Methods
- Hartree-Fock (RHF, UHF, GHF)
- Random Phase Approximation (RPA)
- GW approximation (G0W0, evGW, qsGW)
- Bethe-Salpeter Equation (BSE)
- Coupled Cluster (CCD, CCSD)
- Equation-of-Motion Coupled Cluster
- ADC methods
- Configuration Interaction
- Møller-Plesset Perturbation Theory
Capabilities (CRITICAL)
- One-shot GW (G0W0)
- Eigenvalue self-consistent GW (evGW)
- Quasiparticle self-consistent GW (qsGW)
- BSE for optical excitations
- Molecular GW calculations
- Ionization potentials and electron affinities
- Excitation energies
- Coupled cluster correlation
- Educational/development platform
Key Strengths
GW Methods:
- Multiple self-consistency schemes
- Molecular focus
- Quasiparticle energies
- Spectral functions
- Benchmark quality
BSE Implementation:
- Optical excitations
- Electron-hole interactions
- Absorption spectra
- Exciton binding energies
Research Platform:
- Method development
- Testing new approximations
- Benchmark calculations
- Educational purposes
Clean Implementation:
- Readable Fortran code
- Well-structured
- Easy to modify
- Good documentation
Inputs & Outputs
-
Input formats:
- QUACK input files
- Molecular coordinates
- Basis specifications
-
Output data types:
- Quasiparticle energies
- Excitation energies
- Correlation energies
- Spectral data
Interfaces & Ecosystem
- Integral packages: External integral generation
- Basis sets: Standard basis sets
- Post-processing: Text output parsing
Advanced Features
Self-Consistent GW:
- Partial self-consistency
- Full self-consistency
- Vertex corrections
- Beyond G0W0
BSE Optical Properties:
- Singlet/triplet excitations
- Oscillator strengths
- Exciton analysis
- Optical gaps
Coupled Cluster:
- Ground state correlation
- EOM for excitations
- Comparison with GW/BSE
Performance Characteristics
- Speed: Efficient for molecules
- Accuracy: High-level many-body methods
- System size: Small to medium molecules
- Memory: Standard requirements
- Parallelization: OpenMP threading
Computational Cost
- HF: Fast baseline
- G0W0: O(N^4) with approximations
- evGW/qsGW: Multiple iterations
- BSE: Depends on excitation number
- Typical: Suitable for benchmarks
Limitations & Known Constraints
- System size: Best for small-medium molecules
- Periodicity: Molecular focus only
- Features: Specialized scope
- Community: Research group centered
- Production: More for development/benchmarks
- Gradients: Not available
Comparison with Other Codes
- vs molgw: Similar GW focus, different implementations
- vs BerkeleyGW: QUACK molecular, BerkeleyGW periodic
- vs Turbomole: QUACK more GW variants
- vs ORCA: QUACK specialized GW, ORCA general purpose
- Unique strength: GW method variety, educational platform
Application Areas
Spectroscopy:
- Photoelectron spectra
- Optical absorption
- Ionization energies
- Electron affinities
Method Development:
- Testing GW variants
- BSE approximations
- Vertex corrections
- Benchmark sets
Molecular Properties:
- HOMO-LUMO gaps
- Fundamental gaps
- Optical gaps
- Quasiparticle renormalization
Best Practices
GW Calculations:
- Appropriate starting point
- Basis set convergence
- Self-consistency level
- Frequency treatment
BSE:
- Number of states
- Kernel approximations
- TDA vs full BSE
- Convergence checks
Community and Support
- Open-source GPL v3
- Active GitHub development
- Academic research group
- Publications and benchmarks
- Growing community
Verification & Sources
Primary sources:
- GitHub repository: https://github.com/pfloos/QuACK
- Loos et al. publications on GW/BSE
- Benchmark studies (GW100, etc.)
- Active development
Confidence: VERIFIED
- Source code: OPEN (GitHub, GPL v3)
- Documentation: Wiki available
- Active development: Yes
- Academic citations: Yes