Nonequilibrium effects in diffusion of interacting particles on vicinal surfaces

Area of Science:

• Surface science
• Condensed matter physics
• Statistical mechanics

Background:

• Collective diffusion is crucial for understanding particle behavior on surfaces.
• Nonequilibrium conditions can significantly alter equilibrium diffusion dynamics.
• Vicinal surfaces with steps present unique challenges for diffusion modeling.

Purpose of the Study:

• To investigate the impact of nonequilibrium conditions on collective diffusion of interacting particles on vicinal surfaces.
• To characterize the time and coverage dependence of the collective diffusion coefficient under nonequilibrium conditions.
• To elucidate the role of step binding and terrace width in influencing diffusion dynamics.

Main Methods:

• Monte Carlo simulations of a lattice-gas model on an ideal stepped surface.
• Modeling adatoms with nearest-neighbor attractive or repulsive interactions.
• Application of the Boltzmann-Matano method to spreading density profiles.

Main Results:

• Observed three distinct stages in collective diffusion coefficient D(xx,C)(t)(theta) for diffusion across steps.
• Identified sharp peaks in D(xx,C)(t)(theta) at intermediate times and specific coverages due to terrace relaxation.
• Noted that nonequilibrium effects are weaker for diffusion along steps, becoming apparent only under suppressed or enhanced diffusion conditions.

Conclusions:

• Nonequilibrium conditions introduce complex, time-dependent behaviors in collective diffusion on vicinal surfaces.
• Step binding and terrace width significantly influence diffusion dynamics, leading to coverage-dependent anomalies.
• The study provides a detailed understanding of diffusion mechanisms on stepped surfaces beyond equilibrium assumptions.