Kinetics of CH + N2 revisited with multireference methods.

Area of Science:

• Chemical Kinetics
• Theoretical Chemistry
• Computational Chemistry

Background:

• The CH + N2 reaction is crucial for understanding prompt nitric oxide (NO) formation.
• Previous theoretical models had discrepancies with experimental data.

Purpose of the Study:

• To reexamine the potential energy surface for the CH + N2 reaction.
• To improve the accuracy of rate coefficient predictions for prompt NO formation.
• To resolve discrepancies between theoretical and experimental results.

Main Methods:

• Multireference ab initio electronic structure methods with large basis sets (up to aug-cc-pvqz).
• Comparison with coupled cluster with singles, doubles, and perturbative triples (CCSD(T)) calculations.
• Transition state theory (TST) calculations, including variable reaction coordinate TST.

Main Results:

• Identified significant shortcomings in single-reference methods for key transition states.
• Revised transition state properties led to order-of-magnitude changes in predicted rate coefficients.
• Two distinct reaction pathways contribute significantly to kinetics at higher temperatures.

Conclusions:

• The revised theoretical predictions align with recent experimental measurements.
• This work provides a more accurate understanding of the CH + N2 reaction kinetics.
• The findings are important for atmospheric chemistry and combustion modeling.