COMPUTER-SIMULATION OF POINT-DEFECT PROPERTIES IN DILUTE FE-CU ALLOY USING A MANY-BODY INTERATOMIC POTENTIAL

The behaviour of copper atoms in dilute solution in alpha-iron is impo rtant for the microstructural changes that occur in ferritic pressure vessel steels under fast-neutron irradiation. To investigate the prope rties of atomic defects that control this behaviour, a set of many-bod y interatomic potentials has been developed for the Fe-Cu system. The procedures employed, including modifications to ensure suitability for simulating atomic collisions at high energy, are described. The effec t of copper on the lattice parameter of iron in the new model is in go od agreement with experiment. The phonon properties of the pure crysta ls and, in particular, the influence of the instability of the metasta ble, bcc phase of copper that precipitates during irradiation are disc ussed. The properties of point defects have been investigated. It is f ound that the vacancy has lower formation and migration energy in bce copper than in alpha-iron, and the self-interstitial atom has very low formation energy in this phase of copper. The threshold displacement energy in iron has been computed as a function of recoil orientation f or both iron- and copper-atom recoils. The differences between the ene rgy for the two species are small.