An ab initio potential surface describing abstraction and exchange for H+CH4

Area of Science:

• Chemical Kinetics
• Computational Chemistry
• Theoretical Chemistry

Background:

• The H+CH4 reaction is fundamental in combustion and atmospheric chemistry.
• Accurate potential energy surfaces (PES) are essential for simulating reaction dynamics.

Purpose of the Study:

• To develop an ab initio-based global potential energy surface (PES) for the H+CH4 system.
• To describe both abstraction and exchange reaction pathways.
• To perform quasiclassical trajectory (QCT) calculations for the H+CD4 reaction.

Main Methods:

• Ab initio electronic structure calculations using the partially spin-restricted coupled-cluster method (RCCSD(T)) with an aug-cc-pVTZ basis set.
• Fitting 20,728 calculated energies to generate the global PES.
• Quasiclassical trajectory calculations for the H+CD4-->HD+CD3 reaction at specific collision energies.

Main Results:

• A permutationally invariant global PES for H+CH4 was developed.
• QCT calculations for H+CD4 reaction dynamics were performed.
• Results were compared with experimental data and density functional theory (DFT) direct dynamics calculations.

Conclusions:

• The developed PES accurately describes the H+CH4 reaction.
• The QCT calculations provide valuable insights into the reaction mechanism and dynamics.
• This work serves as a benchmark for future theoretical and experimental studies.