The trapping of methane on Ir(111): A first-principles quantum study

We implement a fully quantum mechanical study of methane trapping on Ir(111), where the phonons, the molecule-surface interaction, and the molecule-phonon coupling are all computed from first-principles. We find that both the surface corrugation and the phonon coupling vary strongly with molecular orientation and that there is a chemical aspect to this due to the catalytic nature of the metal. For example, molecules with reactive orientations can approach close to surface sites with low barriers to dissociation. Moreover, lattice motion can lower the barrier to dissociation, leading to unusual behavior for the phonon coupling. We find good agreement with experiment and two recent classical studies if we average our potential energy surface over several orientations of the molecule. We also find reasonable agreement with a recent study of methane diffraction, although we show that diffraction does not play a major role in trapping on the smooth Ir(111) surface and that trapping obeys normal energy scaling, consistent with experiment. We show that the trapping probability can be sensitive to the temperature at both high and low incidence energies. Relaxation and desorption of trapped particles are examined.

Automated summary

This study investigates the methane trapping on Ir(111) surface using quantum mechanics, showing the impact of molecular orientation, surface corrugation, and chemical nature of the metal on the trapping mechanism. It also reveals the sensitivity of trapping probability to temperature and the influence of phonon coupling and lattice motion on the trapping behavior. Additionally, the study demonstrates good agreement with experiment and previous research, highlighting the complex interplay of various factors in the trapping process.