Interactions between Methane and Polycyclic Aromatic Hydrocarbons: A High Accuracy Benchmark Study.

Area of Science:

• Computational chemistry
• Materials science
• Physical chemistry

Background:

• Polycyclic aromatic hydrocarbons (PAHs) are fundamental components in various chemical and physical processes.
• Understanding the interaction between PAHs and small molecules like methane is key to fields such as materials science and astrochemistry.
• Previous studies indicated singly coordinated structures as energetically favorable for benzene-methane interactions.

Purpose of the Study:

• To determine the minimum energy structures and interaction energies of methane with a series of PAHs.
• To investigate the shift in preferred coordination geometries for larger PAHs compared to smaller ones.
• To benchmark various density functional theory (DFT) methods against high-level wave-function theory calculations for PAH-methane interactions.

Main Methods:

• High-level electronic structure calculations, including complete-basis-set extrapolated MP2 and CCSD(T) methods.
• Density functional theory (DFT) with dispersion corrections (e.g., -D3) was evaluated.
• Symmetry-adapted perturbation theory (SAPT) was used to analyze interaction components.

Main Results:

• The global minimum energy configuration for methane interacting with naphthalene and larger PAHs shifts from singly to triply coordinated structures.
• Triply coordinated geometries are predicted to be the global minimum for methane on extended systems like graphene and carbon nanotubes.
• The B3LYP functional with the -D3 dispersion correction accurately predicted interaction energies, serving as a benchmark for approximate methods.

Conclusions:

• The coordination preference of methane on PAHs is size-dependent, favoring triply coordinated structures for larger systems.
• This study provides critical data for developing accurate computational methods to model hydrocarbon physisorption on carbon nanostructures.
• The findings have implications for understanding methane adsorption on graphite and related materials.