Atomistic simulations of point defects in ZrNi intermetallic compounds

The properties of point defects, including stable configurations, formation and migration energies, and migration mechanisms, in the ZrNi and Zr₂Ni intermetallic compounds were simulated using molecular dynamics and statics, in conjunction with interatomic potentials derived from the Embedded Atom Method. We describe a method to calculate the formation energy of point defects from the program and apply the method to ZrNi and Zr₂Ni. The results showed that vacancies are most stable in the Ni sublattice, with formation energy of 0.83 and 0.61 eV in ZrNi and Zr₂Ni, respectively. Zr vacancies are unstable in both compounds; they spontaneously decay to pairs of Ni vacancy and antisite defect. The interstitial configurations and formation energies were also calculated, with similar behaviors. In ZrNi, vacancy migration occurs preferentially in the [0 2 5] and [1 0 0] directions, with migration energy of 0.67 and 0.73 eV, respectively, and is essentially a two-dimensional process, in the (0 0 1) plane. In Zr₂Ni, vacancy migration is one-dimensional, occurring in the [0 0 1] direction, with a migration energy of 0.67 eV. In both compounds, the presence of Ni antisite defects decreases the Ni vacancy migration energy by up to a factor-of-three, and facilitates three-dimensional motion.