State-Resolved Dynamics and Rate Coefficients of the F + C₂H₆ Reaction with a Submerged Barrier: Ring Polymer...

Due to its potential applications in HF chemical lasers and its significance as a prototypical polyatomic reaction, the F + C₂H₆ reaction has long been a central topic in chemical kinetics and molecular dynamics. Although previous studies have reported both experimental and theoretical rate constants, discrepancies among these results persist. Moreover, the available experimental data do not cover the full temperature range, particularly at temperatures above room temperature, which are highly relevant to combustion and chemical laser applications. In this work, we report a new FI-NN potential energy surface (PES) developed at the gold-standard CCSD(T) level, which has been validated by its ability to reproduce HF rovibrational state distributions in close agreement with experimental results. Using this PES, we computed rate coefficients over the temperature range of 200-1100 K via direct ring-polymer molecular dynamics (RPMD). The calculated rates show good agreement with available experimental data in the low-temperature regime and extend reliable predictions to the high-temperature region relevant to combustion and chemical laser processes. These accurate RPMD rate coefficients can be combined with quasi-classical trajectory (QCT) calculations to yield reliable state-resolved dynamics and rate coefficients, thereby providing a consistent kinetic description across a broad temperature range.