Revisiting the F + HCl → HF + Cl reaction using a multireference coupled-cluster method

Area of Science:

• Chemical Kinetics
• Quantum Chemistry
• Theoretical Chemistry

Background:

• The F+HCl reaction is a key benchmark system for theoretical studies in chemical dynamics.
• Previous ab initio calculations have struggled to accurately reproduce experimental observations, particularly the reaction barrier height.

Purpose of the Study:

• To construct an accurate potential energy surface (PES) for the F+HCl reaction.
• To investigate the reaction dynamics, including rate constants and product state distributions, using high-level quantum mechanical methods.

Main Methods:

• Internally contracted multireference coupled-cluster (MRCC) method was employed to build the PES.
• A fully converged time-independent quantum mechanical (TIQM) approach was used for dynamics calculations.

Main Results:

• A significantly reduced barrier height of 1.59 ± 0.08 kcal mol⁻¹ was calculated, aligning with experimental estimates.
• Calculated rate constants show excellent agreement with experimental values.
• Qualitative agreement was achieved for vibrational product distributions, highlighting the influence of initial rotational states.

Conclusions:

• The new PES accurately describes the F+HCl reaction dynamics.
• The study provides valuable insights into the factors governing product state distributions in this important reaction system.