Pb/Cu(100) surface superstructures: Monte Carlo and molecular dynamics simulations

Monte Carlo simulations with simple pair potentials of the Lennard-Jones type enable us to show the stability of the three experimentally known superstructures of Pb/Cu (100) at different lead submonolayer coverages: c(4 x 4) at theta=3/8, c(2 x 2) at theta=0.5 and c(5 root 2 x root 2)R45 degrees at theta=0.6. In addition, numerous details of these superstructures, including interatomic distances, surface alloying, corrugation and weak modulation are obtained numerically in quantitative and qualitative accord with the experimentally observed and measured data. By molecular dynamics the melting of these structures is studied from the temperature dependence of the Pb-atom average energy and diffusion coefficient, with evidence for a first-order transition for every superstructure. The dispersion of surface phonons is also derived. (C) 1997 Elsevier Science B.V.