APOST3D

Official Resources

• GitHub: https://github.com/mgimferrer/APOST3D
• Documentation: https://github.com/mgimferrer/APOST3D/blob/master/DOCUMENTATION.md
• Repository License: GPL-3.0
• Recent publication: APOST-3D: Chemical concepts from wavefunction analysis (J. Chem. Phys. 2024)

Overview

APOST3D is an open-source Fortran-based code developed at the Universitat de Girona for extracting chemical concepts from wavefunction analysis. It provides a broad set of chemically motivated descriptors, including atomic populations, bond orders, local spin analysis, and effective oxidation states.

Scientific domain: Wavefunction analysis, bond orders, local spin, oxidation-state analysis
Target user community: Quantum chemists seeking chemically interpretable descriptors from wavefunction post-processing

Theoretical Methods

• Atomic population analysis
• Bond order analysis
• Local spin analysis
• Effective oxidation state analysis
• Wavefunction-derived chemical concept extraction

Capabilities (CRITICAL)

• Open-source wavefunction-analysis code on GitHub
• Calculates atomic populations and bond orders
• Includes local spin analysis and effective oxidation states
• Command-line executable workflow with dedicated documentation
• Uses formatted checkpoint (.fchk) and input files as part of the documented workflow

Sources: GitHub repository, project documentation, and public publication summary

Key Strengths

Broad Chemical-Concept Toolkit:

• Bond orders
• Population analysis
• Local spin descriptors
• Effective oxidation states

Open and Documented:

• GPL-3.0 licensed
• Public GitHub repository
• Dedicated documentation file and usage instructions

Modern Public Availability:

• Active public repository
• Clear build instructions
• Recent literature presence

Inputs & Outputs

• Input formats:

  • .fchk files
  • APOST3D input files as documented in the repository

• Output data types:

  • Atomic populations
  • Bond orders
  • Local spin analysis results
  • Effective oxidation state descriptors

Workflow and Usage

1. Compile the apost3d executable.
2. Prepare name-input.fchk and name-input.inp in the working directory.
3. Run apost3d name-input > name-output.apost.
4. Inspect the resulting chemical descriptors and analysis output.

Performance Characteristics

• Compiled Fortran workflow
• Suited to detailed descriptor extraction from prepared wavefunction data
• Broader chemical-concept scope than many single-purpose bonding-analysis tools

Limitations & Known Constraints

• Input preparation: Requires compatible formatted checkpoint and input files
• Command-line workflow: Less turnkey than some GUI-oriented tools
• Scope: Focused on wavefunction-derived descriptors rather than topology visualization

Comparison with Other Tools

• vs Chemissian: APOST3D is a more dedicated scientific descriptor code with open-source workflow and broader chemically motivated analysis scope
• vs NBO/JANPA: APOST3D emphasizes a wider set of chemical concepts including local spin and oxidation states in addition to bond orders
• Unique strength: Open-source package combining bond orders, local spin, and oxidation-state analysis in one code

Application Areas

• Bond-order analysis
• Local spin characterization
• Effective oxidation-state studies
• Chemically interpretable wavefunction post-processing

Community and Support

• Public GitHub repository and issue tracker
• Open-source GPL-3.0 license
• Documented command-line workflow

Verification & Sources

Primary sources:

1. GitHub: https://github.com/mgimferrer/APOST3D
2. Documentation: https://github.com/mgimferrer/APOST3D/blob/master/DOCUMENTATION.md
3. Repository description and usage instructions

Confidence: VERIFIED

Verification status: ✅ VERIFIED

• Public repository: ACCESSIBLE
• Documentation: AVAILABLE
• License: GPL-3.0
• Primary use case: Wavefunction analysis for bond orders and related chemical concepts