ReaxFF Reactive Force Field for Molecular Dynamics Simulations of Hydrocarbon Oxidation
Abstract
To investigate the initial chemical events associated with high-temperature gas-phase oxidation of hydrocarbons, we have expanded the ReaxFF reactive force field training set to include additional transition states and chemical reactivity of systems relevant to these reactions and optimized the force field parameters against a quantum mechanics (QM)-based training set. To validate the ReaxFF potential obtained after parameter optimization, we performed a range of NVT−MD simulations on various hydrocarbon/O_2 systems. From simulations on methane/O_2, o-xylene/O_2, propene/O_2, and benzene/O_2 mixtures, we found that ReaxFF obtains the correct reactivity trend (propene > o-xylene > methane > benzene), following the trend in the C−H bond strength in these hydrocarbons. We also tracked in detail the reactions during a complete oxidation of isolated methane, propene, and o-xylene to a CO/CO_2/H_2O mixture and found that the pathways predicted by ReaxFF are in agreement with chemical intuition and our QM results. We observed that the predominant initiation reaction for oxidation of methane, propene, and o-xylene under fuel lean conditions involved hydrogen abstraction of the methyl hydrogen by molecular oxygen forming hydroperoxyl and hydrocarbon radical species. While under fuel rich conditions with a mixture of these hydrocarbons, we observed different chemistry compared with the oxidation of isolated hydrocarbons including a change in the type of initiation reactions, which involved both decomposition of the hydrocarbon or attack by other radicals in the system. Since ReaxFF is capable of simulating complicated reaction pathways without any preconditioning, we believe that atomistic modeling with ReaxFF provides a useful method for determining the initial events of oxidation of hydrocarbons under extreme conditions and can enhance existing combustion models.
Additional Information
© 2008 American Chemical Society. Received: October 10, 2007; In Final Form: November 27, 2007. Publication Date (Web): January 16, 2008. This research was supported in part by NSF (DMR-0427177) and ONR (N00014-05-1-0778 and N00014-02-1-0665).Attached Files
Supplemental Material - jp709896w-file002.pdf
Supplemental Material - jp709896w-file003.pdf
Supplemental Material - jp709896w-file004.pdf
Supplemental Material - jp709896w-file005.pdf
Files
Additional details
- Eprint ID
- 78017
- DOI
- 10.1021/jp709896w
- Resolver ID
- CaltechAUTHORS:20170607-153823272
- DMR-0427177
- NSF
- N00014-05-1-0778
- Office of Naval Research (ONR)
- N00014-02-1-0665
- Office of Naval Research (ONR)
- Created
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2017-06-07Created from EPrint's datestamp field
- Updated
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2021-11-15Created from EPrint's last_modified field