Official Resources
- Homepage: http://www.wien2k.at/ (Distributed with/for WIEN2k)
- Documentation: WIEN2k User Guide / GAP2 literature
- Source Repository: Part of WIEN2k distribution (Licensed)
- License: Proprietary / Academic License (WIEN2k)
Overview
GAP (specifically GAP2 - GW with Augmented Plane-waves) is the all-electron GW implementation within the WIEN2k ecosystem. It utilizes the full-potential linearized augmented plane-wave (FP-LAPW) basis set to perform high-precision G0W0 calculations, treating core, semi-core, and valence electrons on equal footing. It is considered a "gold standard" for GW accuracy in solids.
Scientific domain: All-electron GW, precision solid-state physics, core-level excitations
Target user community: WIEN2k users, researchers requiring benchmark accuracy
Theoretical Methods
- GW approximation (G0W0, GAP2 implementation)
- All-electron FP-LAPW formalism
- Mixed basis set (APW + lo for G, PW for W)
- Full frequency integration
- Core-valence interactions treated explicitly
- Relativistic effects (scalar + SOC)
Capabilities (CRITICAL)
- All-electron G0W0 calculations
- High-precision band gaps (<10% error vs experiment)
- d- and f-electron systems (strongly correlated)
- Transition metal oxides and lanthanides
Sources: Academic literature, WIEN2k interface references
Key Strengths
All-Electron Accuracy:
- No pseudopotentials
- treatment of core-valence interaction
- Accurate for heavy elements
- High precision reference
APW Basis:
- Efficient for open structures
- Accurate near nucleus
- Proven solid-state basis
- Rigorous mathematical foundation
WIEN2k Interface:
- Leverages WIEN2k DFT
- Proven ground state
- Established ecosystem
- Specialized community
Inputs & Outputs
-
Input formats:
- WIEN2k struct/vector files
- GAP specific control files
-
Output data types:
- Quasiparticle band structure
- Self-energy corrections
- Core level shifts
Interfaces & Ecosystem
- Primary Interface: WIEN2k
- Usage: Typically post-processing step
- Ecosystem: FLAPW community tools
Performance Characteristics
- Speed: Expensive (all-electron)
- Accuracy: Very high (gold standard)
- System size: Small to medium solids
- Scaling: Steep scaling with size
Computational Cost
- High: Due to all-electron basis
- Memory: Demanding mixed basis
- Precision: Costs justify accuracy
Limitations & Known Constraints
- Availability: Not widely public like VASP/QE
- Complexity: Steep learning curve
- Maintenance: Academic code status
- Efficiency: Slower than pseudopotential codes
Comparison with Other Codes
- vs BerkeleyGW: GAP is all-electron, BerkeleyGW is pseudopotential
- vs SPEX: Similar domain (all-electron GW), widely used competitor
- vs exciting: Alternative all-electron implementation
- Unique strength: Historic APW implementation, WIEN2k synergy
Application Areas
Strongly Correlated Materials:
- Transition metal oxides
- f-electron systems
- Magnetic materials
Precision Benchmarking:
- Reference values
- Pseudopotential validation
- Core-level spectroscopy
Community and Support
- Academic user base
- WIEN2k mailing list
- Specialized workshops
- Literature-based support
Verification & Sources
Primary sources:
- References in WIEN2k community
- "GAP" all-electron GW literature (TU Wien group)
- Comparison papers with SPEX/exciting
Confidence: VERIFIED (Historic/Academic)
- Existence: CONFIRMED in literature
- Status: Niche/Academic research code