POINT-DEFECT AND THRESHOLD DISPLACEMENT ENERGIES IN NI3AL .1. POINT-DEFECT PROPERTIES

The energy and volume change associated with the creation of point defects in Ni3Al have been calculated by computer simulation using a modified version of the many-body potentials of Vitek, Ackland and Cserti. The potentials have been adjusted to provide a better description of the interaction between atoms at separations inside the normal nearest-neighbour spacing. This region is important for interstitial properties and the interaction of atoms in displacement events associated with radiation damage. The properties of point defects in the pure metals Al and Ni are in good agreement with known values. For Ni3Al, the properties of the Ni defects are very close to those found by Caro, Victoria and Averback with the embedded-atom potentials for Ni3Al of Foiles and Daw, and the most stable interstitial, in particular, is the Ni-Ni[100] dumbbell centred on a Ni site in the {100} planes which contain only Ni atoms. For the Al and antisite defects, however, the model used here gives different results. The stable interstitial site is predicted to be the octahedral position in the Ni{100} plane, and the Al atom placed on a Ni site has a much higher energy than the antisite on the Al sublattice. These differences are due essentially to the different treatment of the 'size' of the Al atom in the two models. The potentials employed here have been used to investigate the energy of, and stable defect configurations produced by, threshold displacement events of energetic recoil atoms in Ni3Al; these results are presented in part II.