THE EFFECTS OF MANY-BODY INTERACTIONS ON POINT-DEFECT GENERATION

Point-defect generation by energetic displacement events is known to take place when a lattice atom acquires an energy several times its lattice binding value. In this energy range, many-body effects are important and interatomic pair potentials generally give poor representations of atomic interactions. By applying our newly developed molecular-dynamics code, CASC-MD, we investigate the influence of many-body interatomic interactions on the generation characteristics of point defects. We use a composite interatomic potential that assumes the pair-potential nature at high energies and the many-body nature, based on the embedded-atom formalism, at low energies. It is shown that many-body effects lead to lower directional sensitivity of the displacement threshold surface. For a 60 eV collision cascade in Cu, it is shown that the length of the replacement collision sequence decreases from 6 lattice constants at low temperature (near 0 K) to 1.5 lattice constants near the melting point.