Computer simulation of the reflection of energetic ions from crystal surfaces at glancing incidence

A two-dimensional classical dynamics model for calculation of the reflectio n coefficient for scattering of keV beams at glancing incidence using poten tials with cylindrical symmetry is presented. The target in the model consi sts of a single layer or two layers of atomic strings and reflects the (111 ) surface in the most open [1 (1) over bar 0], direction. The critical tran sverse energy of several primary ions for total reflection (100% reflection ) from the surface is determined for Al, Ag, Au, Cu, Ni and Pt crystal (111 ) surfaces. The results are obtained using cylindrical potentials construct ed from recently updated "individual" ion-surface interaction pair potentia l. We compare the results of the simulation with the 2-D row-model to exper imental data for the energy losses. The model most suitable for describing these data is the Oen-Robinson empirical formula for the inelastic losses. Various expressions for the position-dependent friction force as a function of the local electron density are investigated. For the last simulation, t he electron density is averaged over the atomic rows in a manner similar to the construction of cylindrical potentials according to Lindhard's theory. The simulations with the 2-D row-model are available as a compact computer code with good visualization. (C) 1999 Elsevier Science B.V, All rights re served.