Extensive High-Accuracy Thermochemistry and Group Additivity Values for Halocarbon Combustion Modeling

Standard enthalpies, entropies, and
heat capacities are calculated
for 16 813 halocarbons using an automated high-fidelity thermochemistry
workflow. This workflow generates conformers at density functional
tight-binding (DFTB) level, optimizes geometries, calculates harmonic
frequencies, and performs 1D hindered rotor scans at DFT level, and
computes electronic energies at a Gaussian 4 (G4) level. The computed
enthalpies of formation for 400 molecules show good agreement with
literature references, but the majority of the calculated species
have no reference in the literature. Thus, this work presents G4-computed
thermochemistry for thousands of novel halocarbons. This new data
set is used to train an extensive ensemble of group additivity values
and hydrogen bond increment groups within the Reaction Mechanism Generator
(RMG) framework. On average, the new group values estimate standard
enthalpies for halogenated hydrocarbons within 3 kcal/mol of their
G4 values. A significant contribution toward automated mechanism generation
of halocarbon combustion, this research provides thermochemical data
for thousands of novel halogenated species and presents a self-consistent
set of halogen group additivity values.