PyMultiWFN Development Issues - Phase 3

Version: 3.0 Phase: Advanced Bonding Analysis Date: 2026-02-27 Status: 🎯 PHASE 3 READY TO START

Phase 1-2 Status

Phase 1: Foundation ✅

Issue 1-5: Complete (85-100%)
Test suite: 291 tests passing

Phase 2: Electronic Structure Analysis ✅

Issue 6-19: Complete (100%)
Total tests: 444 passing
Code quality: 0 violations

Phase 3: Advanced Bonding Analysis 🆕

Module 3.1: Advanced Bond Order Methods

Issue 20 - Fuzzy Bond Order Implementation

Priority: HIGH Status: 🎯 READY TO START Progress: 0%

Tasks:

Implement fuzzy atom definition
Calculate fuzzy overlap populations
Compute fuzzy bond orders
Validate against Multiwfn reference

Deliverables:

pymultiwfn/bonding/fuzzy.py
pymultiwfn/bonding/__init__.py
tests/bonding/test_fuzzy_bond_order.py (12 tests)
API documentation

Complexity: Medium Dependencies: Phase 2 electron density ✅

API Example:

from pymultiwfn.bonding import Bonding

bond = Bonding('molecule.fch')
fbo = bond.get_fuzzy_bond_order(atom_i=1, atom_j=2)
print(f"Fuzzy BO: {fbo:.3f}")

Acceptance Criteria:

Correct fuzzy atom boundaries
Accurate bond order values (within 0.01 of Multiwfn)
Handle all bond types (single, double, triple, aromatic)
12 passing tests with diverse molecules

Issue 21 - Intrinsic Bond Order

Priority: HIGH Status: 📋 PLANNED Progress: 0%

Tasks:

Calculate intrinsic bond strength
Implement bond polarity correction
Generate bond order matrix
Compare with Wiberg bond orders

Deliverables:

pymultiwfn/bonding/intrinsic.py
tests/bonding/test_intrinsic_bond.py (10 tests)

Complexity: Medium Dependencies: Phase 2 orbital analysis ✅, Issue 20

API Example:

ibo = bond.get_intrinsic_bond_order(atom_i=1, atom_j=2)
print(f"Intrinsic BO: {ibo:.3f}")

Issue 22 - Delocalization Index (DI)

Priority: HIGH Status: 📋 PLANNED Progress: 0%

Tasks:

Calculate electron pair delocalization
Implement 3-center DI analysis
Compute aromaticity from DI
Generate DI matrices

Deliverables:

pymultiwfn/bonding/delocalization.py
tests/bonding/test_delocalization.py (15 tests)

Complexity: High Dependencies: Phase 2 electron density ✅, Issue 20

API Example:

di = bond.get_delocalization_index(atom_i=1, atom_j=2)
print(f"DI: {di:.3f} e")

Acceptance Criteria:

Accurate DI values (within 0.02 e of Multiwfn)
Handle multi-center bonds
Support aromatic systems
15 passing tests

Module 3.2: Aromaticity Indices

Issue 23 - HOMA Implementation

Priority: HIGH Status: 📋 PLANNED Progress: 0%

Tasks:

Calculate HOMA (Harmonic Oscillator Model of Aromaticity)
Implement EN and α parameters for different bonds
Support polycyclic systems
Validate against reference data

Deliverables:

pymultiwfn/aromaticity/homa.py
pymultiwfn/aromaticity/__init__.py
tests/aromaticity/test_homa.py (10 tests)

Complexity: Medium Dependencies: Phase 2 geometry optimization ✅

API Example:

from pymultiwfn.aromaticity import Aromaticity

aro = Aromaticity('benzene.fch')
homa = aro.calculate_homa(ring_atoms=[1,2,3,4,5,6])
print(f"HOMA: {homa:.3f}")  # ~1.0 for benzene

Issue 24 - NICS Analysis

Priority: HIGH Status: 📋 PLANNED Progress: 0%

Tasks:

Calculate NICS(0) at ring center
Compute NICS(1) 1Å above ring
Implement NICS-ZZ component
Support ghost atom placement

Deliverables:

pymultiwfn/aromaticity/nics.py
tests/aromaticity/test_nics.py (12 tests)

Complexity: Medium Dependencies: Phase 2 magnetic shielding ✅, Issue 23

API Example:

nics = aro.calculate_nics(ring_center, height=1.0)
print(f"NICS(1): {nics:.1f} ppm")

Issue 25 - PDI and FLU Indices

Priority: MEDIUM-HIGH Status: 📋 PLANNED Progress: 0%

Tasks:

Calculate Para-Delocalization Index
Implement FLU (Aromatic Fluctuation Index)
Support heterocyclic systems
Compare with HOMA/NICS

Deliverables:

pymultiwfn/aromaticity/indices.py
tests/aromaticity/test_aromatic_indices.py (10 tests)

Complexity: Medium Dependencies: Module 3.1 (DI) ✅, Issue 22

API Example:

pdi = aro.calculate_pdi(ring_atoms)
flu = aro.calculate_flu(ring_atoms)

Module 3.3: Inter-molecular Interactions

Issue 26 - Hydrogen Bond Analysis

Priority: MEDIUM-HIGH Status: 📋 PLANNED Progress: 0%

Tasks:

Identify hydrogen bonds (geometry + energy)
Calculate H-bond strength
Analyze H-bond directionality
Generate H-bond network

Deliverables:

pymultiwfn/interactions/hbond.py
pymultiwfn/interactions/__init__.py
tests/interactions/test_hbond.py (12 tests)

Complexity: Medium Dependencies: Phase 2 critical points ✅

API Example:

from pymultiwfn.interactions import Interactions

inter = Interactions('dimer.fch')
hbonds = inter.find_hydrogen_bonds()
for hb in hbonds:
    print(f"{hb.donor} -> {hb.acceptor}: {hb.energy:.2f} kcal/mol")

Issue 27 - Halogen Bond Analysis

Priority: MEDIUM Status: 📋 PLANNED Progress: 0%

Tasks:

Detect halogen bonds
Calculate σ-hole properties
Analyze bond strength
Support multiple halogens

Deliverables:

pymultiwfn/interactions/xbond.py
tests/interactions/test_xbond.py (8 tests)

Complexity: Medium Dependencies: Phase 2 electrostatics ✅, Issue 26

Issue 28 - π-π Stacking Analysis

Priority: MEDIUM-HIGH Status: 📋 PLANNED Progress: 0%

Tasks:

Identify π-systems
Calculate stacking geometry
Compute interaction energy
Analyze charge transfer

Deliverables:

pymultiwfn/interactions/pistacking.py
tests/interactions/test_pistacking.py (10 tests)

Complexity: Medium-High Dependencies: Phase 2 electron density ✅, Issue 26

Phase 3 Statistics

Total Issues: 9 new issues (Issue 20-28)

Priority Distribution:

HIGH: 6 issues (Issues 20, 21, 22, 23, 24, 26, 28)
MEDIUM-HIGH: 2 issues (Issues 25, 28)
MEDIUM: 1 issue (Issue 27)

Complexity Distribution:

Medium: 6 issues
Medium-High: 2 issues
High: 1 issue (Issue 22)

Test Coverage Target: +110 tests (444 → 550+ tests)

Duration Estimate: 2-3 months

Dependencies Graph

Phase 2 Electronic Structure ✅
    ↓
    ├─→ Issue 20 (Fuzzy Bond Order)
    │
    ├─→ Issue 21 (Intrinsic Bond Order) ──┐
    │                                      │
    └─→ Issue 22 (Delocalization Index)   │
                                        │
Phase 2 Geometry ✅                       ↓
    ↓                                    Issue 25 (PDI/FLU)
    ├─→ Issue 23 (HOMA)                ↑
    │                                   │
    └─→ Issue 24 (NICS) ────────────────┘
    
Phase 2 Critical Points ✅
    ↓
    ├─→ Issue 26 (Hydrogen Bond)
    │
    ├─→ Issue 27 (Halogen Bond)
    │
    └─→ Issue 28 (π-π Stacking)

Milestones

Milestone 3.1: Bond Order Methods (Week 4)

✅ Issues 20, 21, 22 complete
✅ 37+ new tests
✅ Bond order analysis functional

Milestone 3.2: Aromaticity Indices (Week 8)

✅ Issues 23, 24, 25 complete
✅ 32+ additional tests
✅ Aromaticity analysis available

Milestone 3.3: Inter-molecular Interactions (Week 12)

✅ Issues 26, 27, 28 complete
✅ 30+ new tests
✅ Phase 3 complete

Success Metrics

Code Quality

Test coverage: >90% for Phase 3 modules
Code violations: 0
API stability: No breaking changes after Milestone 3.1

Performance

Fuzzy bond order: <1s for medium molecules
DI calculation: <2s for aromatic systems
H-bond detection: <500ms for dimers

Validation

Multiwfn agreement: >95% of test cases within tolerance
Reference molecule tests: 15+ benchmark molecules
Literature comparison: 8+ published datasets

Immediate Next Steps

This Week

Start Issue 20: Fuzzy Bond Order Implementation
- Set up pymultiwfn/bonding/ module
- Implement fuzzy atom definition
- Write initial tests (12+ tests)
Prepare Phase 3 Infrastructure
- Create module structure
- Set up test fixtures
- Update CI/CD for new modules
Documentation Foundation
- Create bonding analysis outline
- Prepare tutorial structure

Notes

Phase 3 represents advanced chemical analysis capabilities
Focus on quality over speed - each module should be production-ready
Extensive Multiwfn validation required for credibility
Performance optimization integrated throughout

Phase 1 Average: 67% ✅ Phase 2 Target: 100% ✅ ACHIEVED (444 tests) Phase 3 Target: 100% (2-3 months) Overall Project Progress: ~30% (Phase 1-2) → Target 50% (after Phase 3)

Last Updated: 2026-02-27 Next Review: 2026-03-05

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

PyMultiWFN Development Issues - Phase 3

Phase 1-2 Status

Phase 1: Foundation ✅

Phase 2: Electronic Structure Analysis ✅

Phase 3: Advanced Bonding Analysis 🆕

Module 3.1: Advanced Bond Order Methods

Issue 20 - Fuzzy Bond Order Implementation

Issue 21 - Intrinsic Bond Order

Issue 22 - Delocalization Index (DI)

Module 3.2: Aromaticity Indices

Issue 23 - HOMA Implementation

Issue 24 - NICS Analysis

Issue 25 - PDI and FLU Indices

Module 3.3: Inter-molecular Interactions

Issue 26 - Hydrogen Bond Analysis

Issue 27 - Halogen Bond Analysis

Issue 28 - π-π Stacking Analysis

Phase 3 Statistics

Dependencies Graph

Milestones

Milestone 3.1: Bond Order Methods (Week 4)

Milestone 3.2: Aromaticity Indices (Week 8)

Milestone 3.3: Inter-molecular Interactions (Week 12)

Success Metrics

Code Quality

Performance

Validation

Immediate Next Steps

This Week

Notes

FilesExpand file tree

ISSUES_V3.md

Latest commit

History

ISSUES_V3.md

File metadata and controls

PyMultiWFN Development Issues - Phase 3

Phase 1-2 Status

Phase 1: Foundation ✅

Phase 2: Electronic Structure Analysis ✅

Phase 3: Advanced Bonding Analysis 🆕

Module 3.1: Advanced Bond Order Methods

Issue 20 - Fuzzy Bond Order Implementation

Issue 21 - Intrinsic Bond Order

Issue 22 - Delocalization Index (DI)

Module 3.2: Aromaticity Indices

Issue 23 - HOMA Implementation

Issue 24 - NICS Analysis

Issue 25 - PDI and FLU Indices

Module 3.3: Inter-molecular Interactions

Issue 26 - Hydrogen Bond Analysis

Issue 27 - Halogen Bond Analysis

Issue 28 - π-π Stacking Analysis

Phase 3 Statistics

Dependencies Graph

Milestones

Milestone 3.1: Bond Order Methods (Week 4)

Milestone 3.2: Aromaticity Indices (Week 8)

Milestone 3.3: Inter-molecular Interactions (Week 12)

Success Metrics

Code Quality

Performance

Validation

Immediate Next Steps

This Week

Notes