Ordering kinetics in Ni3Al by molecular dynamics

We present molecular dynamics simulations of ordering kinetics in the Ni3Al alloy performed within the embedded atom method (EAM) as a scheme for interatomic potentials. The simulation cell containing 1372 atoms was initially perfectly L12-long-range ordered. After having artificially created one vacancy by removing at random one Ni-atom, the dynamics of the system was simulated at constant temperature and pressure. Atoms are found to migrate predominantly via jumps to nearest-neighbour (nn) vacancies. The number of antisites is low in comparison to the total number of atomic jumps. Therefore most of the jumps are ineffective for ordering kinetics causing only temporary change of the chemical order. Accordingly, the jumps creating antisites are most often followed by reverse jumps. Antisite defects are created as nn antisite pairs. This result is in agreement with predictions based on a model originally formulated within Monte Carlo simulations.