SIMULATION OF POINT-DEFECTS AND THRESHOLD DISPLACEMENTS IN PURE CU AND A DILUTE CU-AU ALLOY

The influence of solute atoms on point-defect properties and defect generation by radiation damage in alloys is known to be important, and hence it is desirable to understand their effect on the basic mechanisms involved. Most computer modeling of these phenomena has only considered pure metals, but as part of a project to investigate displacement cascades in alloys, we have simulated dilute solutions of gold (Au) in copper (Cu), treating this as a ''model'' for a heavy, oversized solute alloy system. In the present paper, modified many-body interatomic potentials for the Cu-Au system are described that are suitable for modeling high-energy atomic collisions. The properties of point defects in pure copper and the dilute alloy, including solute-defect binding energies, are presented. The oversized solute has a larger binding energy with an interstitial atom than with a vacancy. The displacement threshold energy, E(d), of a Cu atom and a Au atom in the copper matrix has been investigated as a function of primary recoil direction, and the difference between the two species is found to be substantial. Furthermore, the presence of a Au solute has a significant effect on the formation of Frenkel pairs by the replacement-collison-sequence mechanism. These results are discussed in terms of the mass and size difference of Cu and Au atoms.