Molecular-dynamics study of surface relaxation, stress, and disordering of Pb(110)

Abstract

Using an empirical many-body Hamiltonian fitted to bulk and surface properties of lead, we have studied the temperature-dependent structural transformations on Pb(110) by molecular-dynamics simulation. The surface is observed to undergo an anomalous thermal expansion prior to disordering at T∼500 K, in good agreement with recent ion-scattering and low-energy electron-diffraction studies. Behavior of the layer-resolved structure factors indicates that the disordering process is anisotropic and occurs in a layer-by-layer fashion. Simulation results are also consistent with experimental observations of surface roughening near 400 K as well as the formation of a quasiliquid surface phase above 500 K. The intrinsic stress anisotropy Δg, present on all fcc (110) surfaces, vanishes at T∼590 K, suggesting the possible existence of a liquid film at the surface. By examination of the structural-anisotropy data taken at various temperatures, we confirmed that complete melting of the surface layer is achieved at ∼590 K. © 1994 The American Physical Society.