Abstract

This project uses the Molecular Dynamics (MD) technique to study the deposition of lead on the (100) face of copper. Integration of the equations of motion is done using the Verlet algorithm. Two potential energy functions axe used to model the particle interactions. The first is a two-body Lennard-Jones potential while the second is a three-body Erko<, potential. The deposition of lead on the (100) face of copper results in the formation of three distinct structures as the coverage is varied. In order of increasing coverage they are : c(4x4), c(2 x 2 ) and c(5\/2 x \/2)R450 reconstructions. The c(4x4) structure is not well understood. It has been ascertained that it ’s structure is that of a single-layer surface alloy. Chains of copper run parallel and alternately with chains of lead. The two most likely structures are the hollow and bridge alloy models. The current project applied the MD technique to determining which of the two structures was the most likely. It turned out that the bridge alloy model was the most likely using Molecular Dynamics. Also a modulation of the alloy copper chains has been documented. This was also studied and the results point to a modulation with an amplitude of around 0.3A and a period of 4 copper-copper distances. Neighbouring alloy copper chains exhibited modulations th a t were 180° out of phase. The structure of the c(2x2) reconstruction is well understood. This structure was included for completeness. The c(5\/2 x \/2)R450 reconstruction has also been the subject of much study in recent years. Starting with an initial hexagonal-type structure the MD simulation evolved the accepted structure for the c(5\/2 x v^2)R45° reconstruction.