MOLECULAR-DYNAMICS SIMULATION OF ELECTRON-IRRADIATION-INDUCED AMORPHIZATION OF NIZR2

We have used molecular-dynamics simulations to examine electron-irradiation-induced amorphization of the ordered intermetallic compound NiZr2. The principal effects of irradiation by MeV electrons, namely chemical disorder and Frenkel-pair generation, were simulated in two separate processes: Chemical disorder was created by exchanging randomly selected Ni and Zr atoms, and Frenkel pairs were introduced by removing atoms at random from their sites and introducing them into interstitial positions. The interactions between the atoms were governed by embedded-atom potentials. During the simulation, the potential energy, volume, radial distribution function, elastic constants, and mean-square atomic displacement were calculated as functions of damage dose. In addition, the structure of the system was characterized by diffraction patterns obtained with the use of the multislice method in conjunction with the simulation. Our results indicate that both random atom exchanges and Frenkel-pair introduction can amorphize NiZr2. At the critical dose of about 0.16 dpa (displacements per atom), the energy and volume attained values corresponding to the quenched liquid and the system became elastically isotropic. Moreover, the variation of the average shear elastic constant with mean-square atomic displacement, following isothermal disorder and isobaric heating, provides evidence in favor of a unified description of amorphization and melting. The results obtained in the present work are in agreement with experimental observations.