Point defect energetics in the ZrNi and Zr₂Ni intermetallics

A systematic study of the properties of point defects has been conducted in the ZrNi and Zr₂Ni intermetallic compounds using molecular dynamics. These properties include the stable defect configurations, formation and migration energies, and vacancy migration mechanisms. Zr vacancies (interstitials) are unstable in both compounds; they spontaneously decay to pairs of Ni vacancy (interstitial) and antisite defect. The stable Ni vacancies have formation energies of 0.83 and 0.61 eV in ZrNi and Zr₂Ni, respectively. In ZrNi, vacancy migration occurs preferentially in the [0 2 5] and [1 0 0] directions, with migration energies 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. The stable interstitial configurations for both compounds consist of a Ni atom lying on the (0 0 1) plane between two out-of-plane nearest-neighbor Zr atoms.