Quantitative Kinetics of HO2Reactions with Aldehydes in the Atmosphere: High-Order Dynamic Correlation, Anharmonicity, and Falloff Effects Are All Important

Bo Long, Yu Xia, Donald G. Truhlar

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


Kinetics provides the fundamental parameters for elucidating sources and sinks of key atmospheric species and for atmospheric modeling more generally. Obtaining quantitative kinetics in the laboratory for the full range of atmospheric temperatures and pressures is quite difficult. Here, we use computational chemistry to obtain quantitative rate constants for the reactions of HO2 with HCHO, CH3CHO, and CF3CHO. First, we calculate the high-pressure-limit rate constants by using a dual-level strategy that combines conventional transition state theory using a high level of electronic structure wave function theory with canonical variational transition state theory including small-curvature tunneling using density functional theory. The wave-function level is beyond-CCSD(T) for HCHO and CCSD(T)-F12a (Level-A) for XCHO (X = CH3, CF3), and the density functional (Level-B) is specifically validated for these reactions. Then, we calculate the pressure-dependent rate constants by using system-specific quantum RRK theory (SS-QRRK) and also by an energy-grained master equation. The two treatments of the pressure dependence agree well. We find that the Level-A//Level-B method gives good agreement with CCSDTQ(P)/CBS. We also find that anharmonicity is an important factor that increases the rate constants of all three reactions. We find that the HO2 + HCHO reaction has a significant dependence on pressure, but the HO2 + CF3CHO reaction is almost independent of pressure. Our findings show that the HO2 + HCHO reaction makes important contribution to the sink for HCHO, and the HO2 + CF3CHO reaction is the dominant sink for CF3CHO in the atmosphere.

Original languageEnglish (US)
Pages (from-to)19910-19920
Number of pages11
JournalJournal of the American Chemical Society
Issue number43
StatePublished - Nov 2 2022

Bibliographical note

Funding Information:
B.L. was supported in part by the National Natural Science Foundation of China (42120104007, 41775125, and 91961123) and by the Science and Technology Foundation of Guizhou Provincial Department of Education, China (KY[2021]014). The work of D.G.T. was supported in part by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award DE-SC0015997. Computational resources were provided by the Minnesota Supercomputing Institute and the National Energy Research Scientific Computing Center.

Publisher Copyright:
© 2022 American Chemical Society.


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