Dissociative adsorption dynamics of nitrogen on a Fe(111) surface

Area of Science:

• Surface Science
• Chemical Physics
• Materials Science

Background:

• Understanding nitrogen molecule (N₂) adsorption and dissociation on transition metal surfaces is crucial for catalysis and materials science.
• Iron (Fe) surfaces, particularly bcc Fe(111), are relevant for industrial applications, necessitating detailed studies of N₂ interaction dynamics.

Purpose of the Study:

• To investigate the dissociative adsorption dynamics of N₂ on clean bcc Fe(111) surfaces.
• To elucidate the mechanisms governing N₂ dissociation at varying impact energies and surface temperatures.
• To compare the dissociation behavior on Fe(111) with other iron surfaces like Fe(110).

Main Methods:

• Utilized a multidimensional potential energy surface constructed from density functional theory (DFT) calculations.
• Employed quasi-classical trajectory (QCT) calculations to compute the dissociative sticking probability.
• Analyzed molecular dynamics, including dissociation pathways, orientation, and location on the surface.

Main Results:

• Theoretical results for normal incidence and impact energies of a few eV align well with experimental data.
• Dissociation is a direct process at higher energies, following narrow reaction paths.
• At lower energies, surface temperature is essential to overcome energy barriers and facilitate dissociation of trapped molecules.
• N₂ dissociation predominantly occurs near the third layer of Fe(111) with molecules oriented parallel to the surface.

Conclusions:

• The dissociative adsorption of N₂ on Fe(111) is energy and temperature-dependent.
• Surface temperature plays a critical role in facilitating dissociation at lower impact energies by enabling trapped molecules to overcome barriers.
• Differences in energy barriers between Fe(111) and Fe(110) surfaces significantly influence N₂ dissociation dynamics, highlighting surface structure sensitivity.