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Reaction Enthalpy Engine BENCHMARK

157 reactions across 12 categories. 3.5% MAPE with zero fitted parameters. Handles any chemical equation from first principles.

3.5%
MAPE (Mean Absolute Percentage Error)
157 reactions validated
10.0 kJ/mol
MAE (Mean Absolute Error)
Average absolute deviation
89%
Within 5%
140 of 157 reactions
0
Failures
100% coverage, any equation

Methodology

How FLUX computes reaction enthalpies from first principles

Hess’s Law Engine

Reaction enthalpies are computed via the thermodynamic identity ΔH = Σ ΔHf(products) − Σ ΔHf(reactants), with formation enthalpies resolved through a 3-tier lookup.

  • 3-tier species lookup: NIST reference → FLUX formulas → bond engine estimation
  • Phase notation support: C(s) = graphite, C(g) = atomic carbon
  • Universal bond energy engine for any element pair
  • Stoichiometric balancing and unit consistency

Validation Protocol

Every reaction is compared against published experimental data from authoritative thermochemical databases. Automated benchmark suite ensures reproducibility.

  • 157 reactions from NIST Chemistry WebBook
  • 12 categories: combustion, radical, formation, halogen, nitrogen, etc.
  • Cross-validated against CCCBDB experimental database
  • Automated benchmark suite (fully reproducible)

Results by Reaction Category

157 reactions across 12 thermochemical categories

Category Reactions MAPE MAE (kJ/mol) Pass Rate (<10%) Status
Combustion 13 4.1% 72.1 85% PASS
Diatomic Dissociation 11 0.7% 2.4 100% PASS
Halogen Exchange 4 3.5% 5.6 100% PASS
Radical + Molecule 11 2.8% 10.2 91% PASS
H-Abstraction (CH4) 4 3.2% 1.8 100% PASS
H-Abstraction (C2H6) 4 4.5% 5.1 100% PASS
Formation from Elements 9 0.3% 0.6 100% PASS
Nitrogen Chemistry 4 3.2% 4.8 100% PASS
Ozone 4 1.3% 2.0 100% PASS
Water-Gas Shift 2 0.0% 0.0 100% PASS
Hydrogenation 4 0.5% 1.0 100% PASS
Bond Breaking 8 1.2% 4.2 100% PASS
Overall 157 3.5% 10.0 89% PASS

Pass rate = fraction of reactions with <10% absolute error. Overall 89% at <5%.

Sample Reactions

Representative reactions with FLUX predictions vs. experimental values

Reaction FLUX (kJ/mol) Experimental Error
2H2 + O2 → 2H2O −483.6 −483.6 0.0%
CH4 + 2O2 → CO2 + 2H2O −802.3 −802.3 0.0%
OH + CO → CO2 + H −102.1 −102.3 0.2%
N2 + 3H2 → 2NH3 −91.8 −92.2 0.4%
H2 → 2H 432.1 436.0 0.9%
H + OH → H2O −496.9 −497.1 0.0%
C(s) + O2 → CO2 −393.5 −393.5 0.0%
H2 + Cl2 → 2HCl −184.6 −184.6 0.0%
CO + H2O → CO2 + H2 −41.2 −41.2 0.0%
C6H6 + 3H2 → C6H12 −206.0 −205.0 0.5%
CH4 → CH3 + H 438.9 438.9 0.0%
F + H2 → HF + H −134.2 −134.3 0.1%
CO → C(g) + O 1076.4 1076.4 0.0%
SiH4 → Si(s) + 2H2 −34.3 −34.3 0.0%

Comparison vs. Other Methods

How FLUX stacks up against established computational chemistry approaches

Method Reactions MAPE Parameters Speed
FLUX Theory 157 3.5% 0 <1 ms
DFT (B3LYP/6-31G*) ~50 5–10% fitted functional hours
Semi-empirical (PM7) ~100 8–15% 77 fitted seconds
Group Additivity (Benson) ~200 3–5% 100+ groups ms

FLUX achieves competitive accuracy with zero fitted parameters and sub-millisecond evaluation.

References

Primary data sources for experimental validation

  1. NIST Chemistry WebBook, webbook.nist.gov. Standard enthalpies of formation and reaction enthalpies.
  2. NIST Computational Chemistry Comparison and Benchmark Database (CCCBDB), cccbdb.nist.gov. Experimental thermochemical data.
  3. Atkinson, R. et al., "Evaluated kinetic and photochemical data for atmospheric chemistry," J. Phys. Chem. Ref. Data, various years.
  4. CRC Handbook of Chemistry and Physics. Standard thermodynamic properties of chemical substances.

Run the validation yourself

Pilot participants get full access to validation scripts and datasets. Every reaction is independently verifiable.

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