Workspace Structure

OpenQuantum is a multi-crate Cargo workspace of 11 crates:

crates/
├── common/       # Core data types (Molecule, BasisSet, ScfResult), error types, linalg
├── basis/        # Basis set loading, normalization, ECP parsing, .obs embedded files
├── integral/     # One- and two-electron integrals (MD, SP fast paths, Rys quadrature), ECP, gradients, Hessians
├── symmetry/     # Point group detection, character tables, irrep assignment
├── dft/          # Kohn–Sham DFT: exchange-correlation functionals, grid integration, dispersion
├── solvent/      # Implicit solvent models: PCM-family, ddCOSMO/ddPCM, SMD
├── iooq/         # Input file parsing (section-based format)
├── scf/          # RHF/UHF/ROHF + RKS/UKS solvers, DIIS, Fock builder, CPHF, analytic gradients/Hessians
├── posthf/       # MP2 and CCSD(T) correlation energies
├── geometry/     # BFGS/RFO/IC optimization, IRC, NEB, harmonic frequencies, thermochemistry
└── driver/       # Binary entry point (oquantum), pipeline dispatch, checkpoint

Dependency Graph (acyclic)

common (root)
  ├─ basis
  │    └─ integral ────────────────────────────────────┐
  ├─ symmetry ─────────────────────────────────────────┤
  ├─ dft ──────────────────────────────────────────────┤
  ├─ solvent (depends on common, dft, integral) ───────┤
  ├─ iooq ─────────────────────────────────────────────┤
  ├─ geometry ─────────────────────────────────────────┤
  │                                                     ▼
  └─ scf ── posthf ── driver ──────────────────────────┘

Crate Descriptions

Crate	Role	Key Exports
`common`	Root crate: error types, linalg, shared data types	`Molecule`, `Atom`, `BasisSet`, `Shell`, `Primitive`, `ScfOptions`, `ScfResult`, `OneElectronIntegrals`, `IntegralProvider`, `ReactionField`, `CoordinateUnit`, `OpenQuantumError`
`basis`	Basis set loading & storage, normalization, ECP parsing	`load_basis_set`, `ecp::load_ecp_library`, `cartesian_to_pure_tmatrix`
`integral`	1e/2e integrals, ECP & gradient integrals, ERI Hessians	`compute_one_electron_integrals`, `TwoElectronIntegrals`, `DirectScfIntegrals`, `shell_quartet_eri`, `shell_quartet_eri_hessian`, `ecp::build_ecp_matrix_from_molecule`
`symmetry`	Point group detection, symmetry operations	`detect_symmetry`, `PointGroup`, `SymmetryInfo`
`dft`	Kohn–Sham DFT: functionals, grid, XC integration, dispersion	`Functionals`, `functional`, `FunctionalSpec`, `MolecularGrid`, `GridLevel`, `integrate_xc`, `build_xc_matrix`, `build_unrestricted_xc_matrices`, `dispersion_energy`, `DispersionModel`
`solvent`	Implicit solvation: PCM, ddCOSMO/ddPCM, SMD, gradients, Hessians	`PcmSolver`, `DdSolver`, `SmdCds`, `build_surface`, `pcm_matrices`, `pcm_gradient`, `pcm_hessian`, `ddcosmo_gradient`
`scf`	RHF/UHF/ROHF/RKS/UKS solvers, DIIS, Fock builder, output, checkpoint, CPHF, analytic gradients/Hessians	`rhf_scf`, `uhf_scf`, `rohf_scf`, `rks_scf`, `uks_scf`, `rks_scf_range_separated`, `rks_scf_with_reaction_field`, `uks_scf_with_reaction_field`, `DiisAccelerator`, `checkpoint::{save,load}`
`posthf`	MP2 and CCSD(T) correlation energy	`mp2_correlation_energy`, `ccsd_energy`, `ccsdt_energy`
`iooq`	Input file parsing (section-based format)	`Route`, `Method`, `RunType`, `parse_molecule`, `Route::parse`
`geometry`	BFGS optimization, Berny RFO, GDIIS/GEDIIS, harmonic frequencies, IRC, NEB	`optimize`, `OptimizationResult`, `frequencies`, `frequencies_from_hessian`, `FreqResult`
`driver`	Binary entrypoint, pipeline dispatch, checkpoint	`prepare_scf`, `run_pipeline`

Commands

Action	Command
Build all	`cargo build --release`
All tests	`cargo test`
Single crate	`cargo test -p <name>`
Run input	`cargo run --release --package oquantum -- <input_file>`
Documentation	`cargo doc --no-deps`

Note: cargo run requires --package oquantum (or -p oquantum) because the workspace has multiple crates. The binary's name is oquantum.