Surface dynamics on submonolayer Pb/Cu(001) surfaces

Area of Science:

• Surface Science and Materials Science
• Computational Condensed Matter Physics

Background:

• Understanding the atomic structure and dynamics of adsorbed layers is crucial for surface science.
• The behavior of submonolayer Pb on Cu(001) is complex, involving various two-dimensional phases.
• Phonon spectra provide insights into the dynamic stability and vibrational properties of surfaces.

Purpose of the Study:

• To investigate the interplay between atomic structure and phonon spectra of Pb phases on Cu(001).
• To determine how Pb coverage influences the dynamic stability and vibrational modes of the Pb/Cu(001) system.
• To explore the formation of new adsorbate-substrate vibration modes with increasing coverage.

Main Methods:

• Embedded Atom Method (EAM) interatomic potentials for calculating atomic structure and phonon spectra.
• Density Functional Theory (DFT) for complementary calculations of equilibrium atomic structures.
• Analysis of phonon modes, including the Rayleigh mode of the copper surface.

Main Results:

• Dynamic stability of Pb/Cu(001) structures increases with coverage, from 0.375 ML to 0.6 ML.
• A dense Pb layer formed at 0.6 ML exhibits enhanced dynamic stability.
• Increasing Pb coverage shifts the copper surface's Rayleigh mode to higher energy.
• New mixed adsorbate-substrate vibration modes appear with increasing coverage.

Conclusions:

• Coverage-dependent structural and dynamic properties are significant for Pb/Cu(001) systems.
• The formation of dense Pb layers leads to increased dynamic stability.
• Adsorbate-substrate interactions modify surface phonon behavior, creating new vibrational modes.