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

Abstract

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.

Computational thermochemistry: extension of Benson group additivity approach to organoboron compounds and reliable predictions of their thermochemical properties

“…In some instances, such as with organosilicon compounds, 31 inconsistencies in the reference data have completely prevented the determination of an internally consistent set of group contributions by experimental means. As shown by us 32,33 and by others, [103][104][105][106][107] a simple fix to the problem is offered by theoretical approaches and high-level composite methods in particular. In the following, we pursue this avenue and determine Benson group contributions for boron using the high-level W1X-1 data in Table 1.…”

RMG Database for Chemical Property Prediction

“…RMG’s group additivity scheme is broadly based on that developed by Benson et al H f298 , S f298 , and C p ( T ) at a set of temperatures for a given molecule are defined by summing a contribution from each heavy atom in the molecule. In the 20 th century, most of these group values were derived from the experimental data, but in the last 20 years, a much larger set of group values has been derived from quantum chemical calculations. − RMG’s scheme also integrates several advanced corrections to the ordinary Benson groups: radical corrections using the hydrogen bond increment method adopted from Lay et al 1995 ring and polycyclic strain corrections using the method of Han et al 2018. , long-distance interaction corrections for non-cyclic gauche 1,4 and 1,5 interactions. long-distance interaction corrections for halogenated molecules …”

“…In the 20 th century, most of these group values were derived from the experimental data, but in the last 20 years, a much larger set of group values has been derived from quantum chemical calculations. − RMG’s scheme also integrates several advanced corrections to the ordinary Benson groups: radical corrections using the hydrogen bond increment method adopted from Lay et al 1995 ring and polycyclic strain corrections using the method of Han et al 2018. , long-distance interaction corrections for non-cyclic gauche 1,4 and 1,5 interactions. long-distance interaction corrections for halogenated molecules ortho, para, and meta cyclic non-nearest-neighbor interactions using values from Ince et al 2015 and Ince et al 2017. , ketene corrections …”

“…An additional neural network-based thermochemistry estimator specific for halogenated species was trained off of G4 data from Farina et al 2021 recently. ,, While not yet added to the RMG database, this neural network will be available in the near future.…”

“…Species involving both nitrogen and sulfur are available in primaryNS, and many important aromatic species are available in SABIC_aromatics, SABIC_aromatics_1dHR, and SABIC_aromatics_1dHR_extended. For halogen chemistry, the CHOX_G4 (X = F, Cl, Br, FCl, ClBr, and FClBr) libraries are recommended as they cover a significant portion of their respective chemical spaces with up to four carbons and oxygen atoms . Catalyst adsorbates are available in SurfaceThermoPt111 and SurfaceThermoNi111. , Many other specialized thermo libraries are also available within the RMG database.…”