MOLECULAR-DYNAMICS SIMULATIONS OF A 10-KEV CASCADE IN BETA-NIAL

Molecular dynamics computer simulations were employed to investigate defect production, atomic mixing and chemical disordering in beta-NiAl owing to 10 keV cascades. The embedded atom potentials of Voter and Chen (1989) were employed. Point defect energies and threshold displacement energies were also obtained. The defect production efficiency for the 10 keV cascade was 0.27, which is somewhat larger than that found in simulations of metals with a f.c.c. structure. No interstitial clustering and very little vacancy clustering were observed. The threshold displacement energy is lowest for Ni atoms recoiling along [100], 34 eV, followed by the [110], approximate to 54 eV, and [111], approximate to 130 eV. The [111] crowd-ion is the stable interstitial defect. The mixing parameter was small, 6.8 Angstrom(5)/eV. Efficient chemical disordering was nevertheless observed near the centre of the cascade; there the short range order parameter was reduced to 0.24. Statistical methods were developed to follow the atomic structure during the evolution of the cascade and to describe the chemical disorder.