Classical studies of H atom trapping on a graphite surface.

Area of Science:

• Surface science
• Computational chemistry
• Atomic physics

Background:

• Understanding atom-surface interactions is crucial for fields like materials science and astrophysics.
• The sticking of hydrogen isotopes on graphite is a key process in fusion energy research and interstellar chemistry.

Purpose of the Study:

• To investigate the trapping and sticking mechanisms of hydrogen (H) and deuterium (D) atoms on the graphite (0001) surface.
• To develop a detailed potential energy surface for atom-surface interactions.
• To compute trapping cross sections and estimate sticking probabilities.

Main Methods:

• Utilized density functional theory (DFT) for total electronic energy calculations.
• Developed a 3D potential energy surface accounting for atom motion and surface atom reconstruction.
• Employed classical methods to compute trapping cross sections as a function of incident energy.
• Investigated the role of lattice degrees of freedom and impact parameters on trapping.

Main Results:

• Identified long-lived trapping resonances for H and D atoms on graphite.
• Found that trapping probability increases with additional lattice degrees of freedom and larger impact parameters.
• Calculated a maximum trapping cross section of 0.2 Ų at 1 ps for H atoms with 0.3 eV energy.
• Estimated lower bounds for H and D sticking probabilities at 0.024 and 0.050, respectively.

Conclusions:

• The C-H bond's rapid dissociation necessitates energy dissipation mechanisms for efficient sticking.
• Long-lived trapping resonances and increased lattice interactions significantly enhance atom trapping.
• Calculated sticking probabilities are an order of magnitude lower than experimental values, suggesting limitations in the current model or experimental conditions.