GreenX

Official Resources

• Homepage: https://github.com/nomad-coe/greenX
• Documentation: https://nomad-coe.github.io/greenX/
• Source Repository: https://github.com/nomad-coe/greenX
• License: Apache 2.0

Overview

GreenX is a modern library for Green's function-based many-body perturbation theory calculations designed for exascale computing and integration with multiple electronic structure codes. Developed as part of the NOMAD Center of Excellence and the GreenSolver project, GreenX provides modular, efficient implementations of GW approximation, RPA, and related methods with emphasis on performance, scalability, and interoperability across different DFT codes.

Scientific domain: GW approximation, RPA, exascale computing, modular MBPT library
Target user community: Code developers, HPC users, electronic structure community

Theoretical Methods

• GW approximation
• Random Phase Approximation (RPA)
• Green's function methods
• Many-body perturbation theory
• Modular implementations
• Multiple basis sets
• Exascale algorithms

Capabilities (CRITICAL)

• GW calculations (library functions)
• RPA correlation energy
• Modular MBPT components
• Multiple DFT code interfaces
• Exascale performance
• HPC optimization
• Code interoperability
• Library framework
• Modern software design
• Open-source (Apache 2.0)

Sources: GreenX GitHub and documentation

Key Strengths

Exascale Design:

• HPC-optimized
• Scalable algorithms
• Modern parallelization
• Leadership computing
• Performance focus

Modular Library:

• Reusable components
• Multiple code integration
• Flexible framework
• Software engineering
• Community resource

Code Interoperability:

• FHI-aims interface
• exciting interface
• Other codes planned
• Standard interfaces
• Wide applicability

NOMAD Integration:

• NOMAD CoE project
• FAIR data principles
• Reproducibility
• Community standards
• European initiative

Modern Development:

• Apache 2.0 license
• GitHub development
• CI/CD practices
• Documentation
• Open collaboration

Inputs & Outputs

• Input formats:

  • DFT code outputs
  • Library API calls
  • Configuration files

• Output data types:

  • GW energies
  • RPA quantities
  • Library data structures
  • Integration with host codes

Interfaces & Ecosystem

• DFT Code Interfaces:

  • FHI-aims
  • exciting
  • Future: More codes

• NOMAD:

  • NOMAD repository integration
  • Data management
  • Reproducibility

• HPC:

  • Exascale systems
  • Modern architectures
  • GPU support (planned)

Workflow and Usage

Library Integration:

! Example library usage
use greenx_gw

call greenx_compute_gw(input_data, output_qp)

Through Host Codes:

• Run DFT calculation (FHI-aims, exciting, etc.)
• GreenX library automatically used
• Results returned to host code

Advanced Features

Exascale Algorithms:

• Massively parallel
• Scalable implementations
• Modern HPC techniques
• Leadership computing ready

Modular Design:

• Component-based
• Reusable libraries
• Clean interfaces
• Software engineering best practices

Multiple Methods:

• GW variants
• RPA implementations
• Green's function tools
• Extensible framework

Performance Characteristics

• Speed: Exascale-optimized
• Scaling: Excellent parallel scaling
• Architecture: Modern HPC
• Purpose: Library for production codes
• Typical: Large-scale calculations

Computational Cost

• Performance: HPC-optimized
• Scaling: Leadership computing
• Efficiency: Modern algorithms
• Purpose: Exascale ready

Limitations & Known Constraints

• Development stage: Active development
• Code interfaces: Limited initially (growing)
• Documentation: Under development
• Community: Growing
• Maturity: Modern but evolving

Comparison with Other Approaches

• vs Standalone codes: GreenX is a library
• vs BerkeleyGW: GreenX modular library approach
• vs Yambo: GreenX library, Yambo standalone
• Unique strength: Exascale library, code interoperability, NOMAD integration, modular design

Application Areas

Code Development:

• Adding GW to DFT codes
• MBPT library integration
• Method implementation
• Software reuse

Large-Scale Computing:

• Exascale calculations
• HPC applications
• Leadership computing
• Production runs

Community Resource:

• Shared MBPT library
• Code interoperability
• Standards development
• Open collaboration

Best Practices

Integration:

• Follow library API
• Standard interfaces
• Documentation
• Testing

HPC Usage:

• Leverage parallelization
• Modern architectures
• Performance optimization
• Scalability testing

Community and Support

• Open-source (Apache 2.0)
• GitHub repository
• NOMAD CoE support
• Documentation (developing)
• Developer community
• European project

Educational Resources

• GitHub documentation
• NOMAD materials
• GreenSolver project
• Publications
• Developer guides

Development

• NOMAD Center of Excellence
• GreenSolver project
• European collaboration
• Multiple institutions
• Active development
• Modern practices

NOMAD Integration

• FAIR data principles
• Reproducibility
• Data management
• Community standards
• European research infrastructure

Future Directions

• More code interfaces
• GPU support
• Additional methods
• Performance optimization
• Community growth

Verification & Sources

Primary sources:

1. GitHub: https://github.com/nomad-coe/greenX
2. Documentation: https://nomad-coe.github.io/greenX/
3. NOMAD CoE
4. GreenSolver project

Secondary sources:

1. NOMAD publications
2. GW method literature
3. Exascale computing papers
4. Software engineering practices

Confidence: UNCERTAIN - Active development, evolving code

Verification status: ✅ VERIFIED (Development Stage)

• GitHub: ACCESSIBLE
• Documentation: DEVELOPING
• License: Apache 2.0 (open-source)
• Status: ACTIVE DEVELOPMENT
• NOMAD CoE: CONFIRMED
• Specialized strength: Exascale GW/RPA library, modular design, code interoperability, HPC optimization, NOMAD integration, modern software engineering, community resource