Molecular dynamics simulations of the primary irradiation damage in Zirconium

Atom-scale numerical calculations were performed to investigate the damage behavior in close-packed hexagonal zirconium (HCP-Zr) by primary irradiation through a molecular dynamics (MD) study. The influences of Primary Knock-on Atom (PKA) energy (EPKA), the PKA incident direction and the ambient temperature (T) on the cascade collision were studied comprehensively. The results show that the athermal recombination corrected displacements per atom (arc-dpa) model is more accurate in comparison with the Norgett-Robinson-Torrens (NRT) model when predicting the steady vacancy (Ns). It was found that the vacancy peak (Npeak), the peak time (tpeak), and the steady time (ts) increase as EPKA and T increase. The steady vacancy also increases with the increase of EPKA. It was also found that Ns increases and subsequently decreases by increasing T, suggesting that there is a suitable temperature to maximize Ns when EPKA is constant. In addition, it was discovered that the PKA incident direction has little effect on vacancy dynamic history. It was proved that EPKA can worsen the irradiation damage in crystal Zr, but T can relieve such damage. In addition, the incident direction was found to have an insignificant effect on the damage. This study highlights that the steady vacancy concentration (C) can characterize the material irradiation damage.