LOW-ENERGY CLUSTER-IMPACT SIMULATED BY MOLECULAR-DYNAMICS - ANGULAR-DISTRIBUTION OF SPUTTERING YIELD AND IMPACT UNDER VARIOUS IMPACT ANGLES

The collision process of low energetic gold atoms and solid targets ha s been simulated using our molecular dynamics simulation code CLIMPACT II. The used algorithm is a third-order predictor Verlet algorithm [L . Verlet, Phys. Rev. 159 (1967) 98; W.F. van Gusteren and H.J.C. Beren dsen, in: Molecular Liquids - Dynamics and Interfaces, AJ. Barnes et a l., eds. (Reidel, 1984) p. 475.]. The iteration time step is continuou sly optimized by the program. About 50% of the total computer time is spent to integrate the motions during the first 100 fs of simulation t ime [B. Nitzschmann, Diploma thesis, Univ. of Oldenburg, Germany, 1992 )] When the crater formation ends and the motions in the target are sl ower, the step increases up to 20 times the start step size. Using thi s algorithm we are able to simulate a target of up to 105 particles. W e use new nonreflecting boundary conditions. Only mechanical interacti ons are considered. The projectile can be chosen as a cluster with var iable impact angle. Specifically the output yield under different impa ct angles and the distribution of the desorbed particles are presented and discussed. The temporal development of the desorption shows three distinct processes: an early explosive process, a surface ablation by an apparent surface shock wave, a final thermal evaporation.