AN INSTANTANEOUS INELASTIC ENERGY-LOSS ALGORITHM FOR USE IN MOLECULAR-DYNAMICS SIMULATIONS

We have developed an instantaneous inelastic energy loss algorithm for use in molecular dynamics simulations of sputtering. This algorithm u ses distance-of-closest-approach (DCA) criteria to initiate inner-shel l electronic excitation, and subsequent removal of the excitation ener gy following hard atom-atom and ion-atom collisions. The DCA criteria used in the algorithm are based on the electron promotion models of Fa no and Lichten [Phys. Rev. Lett. 14 (1965) 627] and Barat and Lichten [Phys. Rev. A 6 (1972) 211]. The amount of energy removed in these har d atom-atom and ion-atom collisions is determined by the energy needed to excite one or more inner-shell electrons to the continuum. This al gorithm has been used to stimulate inelastic energy loss effects for t he Ar+-Cu(100) and Ar+-Cu(111) systems at bombarding energies between 1 keV and 5 keV. Significant reductions in sputtering yields are produ ced above a bombarding energy threshold of approximately 2 keV. Polar- angle distributions of atoms sputtered from the Cu(100) surface also a re changed significantly by this instantaneous inelastic energy loss m odel.