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 Cross-validation:  H2O / RHF / 6-31G* — vibrational frequencies
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Calculator availability:
  gamess_us  ✗ missing    (Python wrapper present, but 'rungms' not on $PATH — install the GAMESS_US binary)
  gaussian   ✗ missing    (Python wrapper present, but 'g16' not on $PATH — install the GAUSSIAN binary)
  nwchem     ✗ missing    (Python wrapper present, but 'nwchem' not on $PATH — install the NWCHEM binary)
  orca       ✓ available  (/Users/mpei/mpei-documents/orca_6_1_1_macosx_arm64_openmpi411/orca)
  psi4       ✗ missing    (Install with `pip install psi4` into the vibe-qc venv, or use the psi4conda env.)
  pyscf      ✓ available  (Python-native)
  qchem      ✗ missing    (Python wrapper present, but 'qchem' not on $PATH — install the QCHEM binary)
  turbomole  ✗ missing    (Python wrapper present, but 'dscf' not on $PATH — install the TURBOMOLE binary)
  vibeqc     ✓ available  (Python-native)

Computing vibe-qc analytic CPHF Hessian (Phase 17b-3)…
Computing ORCA analytic Hessian via ! HF 6-31G* Freq…

  Mode               vibe-qc (cm⁻¹)    ORCA (cm⁻¹)    |Δ|
  ────────────────────────────────────────────────────────────
  bend                     1884.413        1884.908     0.496
  asym stretch             3777.281        3777.561     0.280
  sym stretch              3877.624        3877.713     0.089
  Max |Δω| = 0.496 cm⁻¹

  CSV: examples/ase_compare/output-compare-h2o-vibrations.csv

✓ vibe-qc and ORCA agree on H2O vibrational frequencies to within 5 cm⁻¹ — same CPHF formalism + basis + SCF threshold.