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 uses distance-of-closest-approach (DCA) criteria to initiate inner-shell electronic excitation, and subsequent removal of the excitation energy following hard atom-atom and ion-atom collisions. The DCA criteria used in the algorithm are based on the electron promotion models of Fano 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 hard atom-atom and ion-atom collisions is determined by the energy needed to excite one or more inner-shell electrons to the continuum. This algorithm has been used to stimulate inelastic energy loss effects for the Ar^+-Cu(100) and Ar^+-Cu(111) systems at bombarding energies between 1 keV and 5 keV. Significant reductions in sputtering yields are produced above a bombarding energy threshold of approximately 2 keV. Polar-angle distributions of atoms sputtered from the Cu(100) surface also are changed significantly by this instantaneous inelastic energy loss model.