Molecular dynamics simulations to assess the radiation resistance of different crystal orientations of diamond under neutron irradiation

Abstract

The evolution of defects in diamond under neutron irradiation was studied via molecular dynamics simulation, with under temperatures of 300–1600 K, primary knock-on atom (PKA) energies of 1–5 keV, and incident orientations in [111], [110], and [100]. The results reveal that the formation of Frenkel pairs is insensitive to temperature but strongly dependent on PKA energy and direction. While interstitials are difficult to cluster in diamond, the size and number of vacancy clusters correlate positively with the PKA energy. Moreover, a decrease in thermal spikes is observed, which is ascribed to the fact that most interstitials can bond with surrounding carbon atoms, which prevents them from moving back to the vacancy in the [111] and [100] directions. Consequently, thermal spikes decrease or disappear as the energy increases. This trend shows directional differences. The radiation resistance of diamond with respect to the direction is [110] > [111] > [100] below 1000 K, and [110] > [111] ≈ [100] at temperatures higher (1600 K). This research can be applied in radiation damage prediction and the radiation-related defect interpretation of diamonds.