SEAMM Thermochemistry Reference Library (enthalpies of formation)

Enthalpies of formation of gas-phase species that the Active Thermochemical Tables (ATcT) lack, for the reference species of the connectivity-based hierarchy (CBH) thermochemistry in SEAMM (Simulation Environment for Atomistic and Molecular Simulations). SEAMM's Thermochemistry step takes each reference species from ATcT first and from this library only when ATcT lacks it; results that use it are labelled as mixed.

The library keeps every value each source gives, with its original citation and its uncertainty as stated; the value chosen per species and source and the rule that chose it; any decision by a person (who, when and why); and the derivation of each derived value. Rules: an estimate is never chosen without a recorded decision; a later source replaces an earlier one only when three times as precise and in agreement; values whose measurements disagree beyond three times their combined uncertainty are held; ions are in ATcT's stationary-electron convention. Each source's rms offset from ATcT, measured over species both have, is recorded and added to its uncertainties.

This version (2026.11.12): 85 species with a chosen value and 149 values in all, from these sources, in rank order:

• JANAF-1998: NIST-JANAF Thermochemical Tables, 4th ed., M. W. Chase, J. Phys. Chem. Ref. Data Monograph 9 (1998) (13 values; offset from ATcT 0.38 kJ/mol rms over 10 species)
• derived: Values derived from evaluations (1 values)
• CODATA-1989: J. D. Cox, D. D. Wagman and V. A. Medvedev, CODATA Key Values for Thermodynamics (Hemisphere, 1989) (20 values; offset from ATcT 0.69 kJ/mol rms over 8 species)
• NBS-82: D. D. Wagman et al., The NBS Tables of Chemical Thermodynamic Properties, J. Phys. Chem. Ref. Data 11, Suppl. 2 (1982) (6 values; offset from ATcT 2.81 kJ/mol rms over 10 species)
• D0: Spectroscopic dissociation energies (2 values)
• W4-17: A. Karton, N. Sylvetsky and J. M. L. Martin, J. Comput. Chem. 38, 2063 (2017) (6 values)
• WebBook-SRD69: NIST Chemistry WebBook, NIST Standard Reference Database 69, eds. P. J. Linstrom and W. G. Mallard, https://webbook.nist.gov (values cited to the original measurements) (45 values; offset from ATcT 1.16 kJ/mol rms over 9 species)

Held pending a computed arbitration: 1H-Imidazole, Naphthacene, Isoxazole.

The values are reproduced from, and cite, their original sources: please cite those as well as this record. The NIST-JANAF tables (SRD 13), the NBS tables and the NIST Chemistry WebBook (SRD 69) are credited to the National Institute of Standards and Technology.

Files: references-official.db (SQLite; tables source, species, measurement, reference, derivation, calibration) and references-official.db.report.json (the build report).