Temperature effects on radiation damage in HCP-zirconium: A molecular dynamics study using a fine-tuned machine-learned potential

Abstract

Zirconium has become an indispensable material in nuclear reactors due to its excellent corrosion resistance and low neutron absorption cross section. In this study, we fine-tune an efficient machine-learned interatomic potential for the pure Zr system. This potential demonstrates better performance in predicting defect properties, allowing us to conduct a comprehensive investigation of primary radiation damage through molecular dynamics simulations. We explore the threshold displacement energies of Zr at different temperatures and find that the variation in $E_d$ with temperature is closely related to defect migration and recombination process. A series of cascade simulations with primary knock-on atom energies from 1 to 40 keV is conducted to investigate the effect of temperature on defect generation and clustering behavior in pure Zr. The results show that 10 keV serves as a critical value which large vacancy cluster begins to emerge, revealing distinct regimes of energy-dependence for defects. At low primary knock-on atom (PKA) energies, higher temperatures reduce both the number of steady defects and small-sized clusters. In contrast, at high PKA energies, the steady Frenkel pairs number $N_{\text{s}}$ increases gradually with temperature, along with a greater occurrence of small-sized defect cluster. Moreover, it is likely to form large-sized defect clusters at lower temperature. Our findings provide critical insights into the irradiation damage mechanisms in Zr, offering theoretical guidance for the optimization of its radiation resistance.