Potential Energy Surface for the CH₄-H₂ van der Waals Interaction

Area of Science:

• Atmospheric Chemistry
• Computational Quantum Chemistry
• Molecular Interactions

Background:

• Methane (CH4) is a minor atmospheric component influencing radiative properties.
• Understanding CH4 interactions with other gases is vital for atmospheric models.
• Precise interaction potentials are needed for accurate simulations.

Purpose of the Study:

• To compute the interaction potential between methane (CH4) and hydrogen (H2).
• To provide accurate data for atmospheric radiative transfer calculations.
• To establish a benchmark for CH4-diatomic molecule interactions.

Main Methods:

• Utilized *ab initio* coupled cluster formalism (CCSD(T) and CCSD(T)-F12a).
• Employed extended atomic bases and considered full molecular scattering geometry.
• Compared *ab initio* results with analytic multipolar expansion for long-range interactions.

Main Results:

• Calculated the potential energy surface for CH4-H2 interaction.
• Determined the potential well depth to be -92.92 cm⁻¹.
• Developed a potential suitable for scattering dynamics calculations.

Conclusions:

• Presented the first precise determination of the CH4-H2 interaction potential.
• The computed interaction is intermediate compared to other methane-diatomic interactions.
• This work advances the understanding of atmospheric gas interactions and radiative properties.