பொருள் அறிவியல் & பொறியியல் இதழ்

Irradiation effect Predictions in MgO using Molecular Dynamics Simulations of Incident Single and Multiple Au Ions

Abstract

Benjamin J. Cowen and Mohamed S. El-Genk*

This paper investigates radiation effects in MgO using molecular dynamics (MD) simulations by single, 5 and 10 incident Au ions of energies ranging from 5-20 keV. The simulations employed a splined Buckingham+ZBL potential. The directional dependence of the threshold displacement energies (TDEs) for Frenkel pair formation and the TDE probability distributions for the displacement of an atom are calculated for both PKA types. The determined TDEs corresponding to 50% displacement probability of an atom by O and Mg PKAs are 94 eV and 91 eV, respectively. The effects of radiation by multiple ions are compared to those by 5-50 keV single Au ions. While the length of the produced defect cascade increases proportional to the total energy deposited, the volume of the defect clusters depends on the number of incident ions. For the same total energy, the volumes of the defect clusters produced by multiple incident ions are much larger than with single incident ions. The number of peak and residual defects produced with 10, 5-keV incident ions are an order of magnitude higher than with 5, 20-keV ions. The selected area electron diffraction (SAED) patterns and the radial distribution functions (RDFs) of the results show that 10 incident ions of 10 and 20 keV each, produce significant defects and cause ballistic melting at the peak of the ballistic phase of interaction. After annealing, the irradiated region recrystallizes, with some isolated amorphous pockets remaining. With 10, 20-keV incident ions, a cluster of ≈102,500 vacancies form at the peak of the ballistic phase, however, the number of residual vacancies is approximately 20 times lower. The sizes of the residual vacancy and interstitial clusters appear stable over the 50-100 picoseconds of the performed MD simulations.