Anthraquinone reference benchmark

ThermoScreening can reproduce the DFTB/3ob/COSMO redox-potential tables from Kröll et al., Phys. Chem. Chem. Phys. 24, 2022. The raw calculations and processed tables are published in the immutable Zenodo record 20796838.

Run the benchmark from a source checkout:

python scripts/validate_anthraquinone_zenodo.py

The command:

  • downloads the raw DFTB/3ob/COSMO-DMF outputs and published plot tables;

  • verifies both archives against pinned SHA-256 checksums;

  • processes 13 molecules in three charge states with run_thermo();

  • uses the archived analysis settings, including spin=1 for monoanions and symmetry_number=1 because the historical workflow disabled symmetry analysis;

  • calibrates the parent anthraquinone result against each published table; and

  • compares 13 first-reduction and 12 overall two-electron potentials.

Reference result

Metric

Result

Acceptance limit

Mean absolute error

0.021320 mV

0.05 mV

Maximum absolute error

0.334662 mV

0.5 mV

The largest difference is the first reduction of molecule 7 (1,4-diaminoanthraquinone). The remaining discrepancy is below the precision relevant to the published millivolt-scale table.

Interpretation

This benchmark verifies that ThermoScreening reproduces the archived thermochemistry and redox post-processing when given the same raw electronic energies, frequencies, geometries, spin convention, symmetry number, and reference calibration. It does not establish experimental predictive accuracy.

The archived DFTB_2e column is the calibrated neutral-to-dianion two-electron average. It is reproduced with n_electrons=2 and must not be interpreted as the stepwise anion-to-dianion E2 reported by the current three-state redox workflow. The current workflow calibrates E1 and E2 separately and reports E2e as their arithmetic mean.

The ordinary test suite also retains a compact synthetic anthraquinone fixture. That fixture checks workflow invariants without network access; the Zenodo command is the quantitative external-data benchmark.