Ab initio studies of ClOx reactions: Prediction of the rate constants of ClO + NO2 for the forward and reverse processes

R. S. Zhu, Ming-Chang Lin*

*Corresponding author for this work

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

The potential-energy surface for the reaction of ClO with NO2 has been constructed at the CCSD(T)/6-311 + G(3df)//B3LYP/6-311 + G(3df) level of theory. Six ClNO3 isomers are located; these are ClONO 2, pc-ClOONO, pt-ClOONO, OClNO2, pt-OClONO, pc-OClONO, with predicted energies relative to the reactants of -25.6, -0.5, 1.0, 1.9, 12.2 and 13.6 kcal mol-1, and heats of formation at 0 K of 7.8, 32.9, 34.4, 35.5, 45.6 and 47.0 kcal mol-1, respectively. Isomerizations among them are also discussed. The rate constants for the low-energy pathways have been computed by statistical theory calculations. For the association reaction producing exclusively ClONO2, the predicted low- and high-pressure-limit rate constants in N2 for the temperature range of 200-600 K can be represented by: k1 0(N2) = 3.19 × 10-17 T-5.54 exp-(-384 K/T) cm6 molecule-2 s-1 and k1 = 3.33 × 10-7 T-1.48 exp-(-18 K/T) cm3 molecule-1 s-1. The predicted low- and high-pressure-limit rate constants for the decomposition of ClONO2 in N2 at 200-600 K can be expressed, respectively, by k-1 0 = 6.08 × 1013 T-6.54 exp(-13813 K/T) cm3 molecule-1 s-1 and k-1 = 4.59 × 1023 T-2.43 exp(-13437 K/T) s-1. The predicted values compare satisfactorily with available experimental data. The reverse Cl + NO3 reaction was found to be independent of the pressure, giving exclusively ClO + NO2; the predicted rate constant can be expressed as k(Cl+NO3) = 1.19 × 10-9 T -6.60 exp(58 K/T) cm3 molecule-1 s -1.

Original languageEnglish
Pages (from-to)1514-1521
Number of pages8
JournalChemPhysChem
Volume6
Issue number8
DOIs
StatePublished - 12 Aug 2005

Keywords

  • Ab initio calculations
  • Atmospheric chemistry
  • Isomers
  • Kinetics
  • Reaction mechanisms

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