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Quantum studies of H atom trapping on a graphite surface.
Xianwei Sha1, Bret Jackson, Didier Lemoine
1Department of Chemistry, University of Massachusetts, Amherst, MA 01003, USA.
The Journal of Chemical Physics
|January 11, 2005
Summary
Hydrogen and deuterium atoms can trap on graphite surfaces at low energies. While most atoms scatter, a small fraction remains trapped for extended periods, influencing surface interactions.
Area of Science:
- Surface Science
- Physical Chemistry
- Quantum Mechanics
Background:
- Understanding atom-surface interactions is crucial for catalysis and materials science.
- Chemisorption of hydrogen on graphite requires significant carbon atom displacement.
- Previous models often simplified atomic motion during trapping events.
Purpose of the Study:
- To investigate the trapping and sticking dynamics of hydrogen (H) and deuterium (D) atoms on graphite (0001).
- To model the quantum mechanical behavior of atoms and surface atoms during chemisorption.
- To determine the factors influencing the lifetime and sticking probability of trapped atoms.
Main Methods:
- Utilized a quantum approach incorporating motion for both incident atoms and surface carbon atoms.
- Employed a potential energy surface derived from density functional theory (DFT) calculations.
- Included lattice degrees of freedom quantum mechanically to simulate realistic surface behavior.
Main Results:
- A significant fraction of H or D atoms trap at energies near the chemisorption barrier (0.2 eV).
- Surface carbon atoms reconstruct rapidly (within 50 fs) due to strong forces.
- Most trapped atoms scatter, but 5%-10% persist with picosecond lifetimes, enhanced by lattice interactions.
- Higher incident energies decrease long-term trapping.
Conclusions:
- Quantum modeling reveals complex trapping dynamics for H/D on graphite.
- Surface reconstruction and lattice vibrations play critical roles in atom retention.
- Estimated sticking probabilities approach 0.1 for a fully dissipative system.
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