Dislocation-enhanced experimental-scale vacancy loop formation in hcp Zirconium in one single collision cascade

Area of Science:

• Materials Science
• Nuclear Engineering
• Computational Physics

Background:

• Large defects significantly degrade material properties under irradiation.
• Defect formation is typically attributed to cluster growth or direct ion impact.
• Existing models struggle to explain observed defect densities in low-dose irradiated Zirconium (Zr).

Purpose of the Study:

• To investigate a novel mechanism for large defect formation in irradiated Zirconium (Zr).
• To understand the role of pre-existing dislocations in primary damage production.
• To provide insights into experimental observations in low-dose irradiated Zr.

Main Methods:

• Molecular Dynamics (MD) simulations of collision cascades in hexagonal close-packed (hcp) Zirconium (Zr).
• Analysis of defect nucleation and growth influenced by pre-existing edge dislocations (EDs).

Main Results:

• A pre-existing edge dislocation (ED) significantly promotes vacancy cluster nucleation.
• EDs facilitate the direct formation of experimental-scale vacancy loops (approx. 3 nm) within a single displacement cascade.
• This dislocation-mediated mechanism explains high-density loop formation observed in low-dose irradiated Zr.

Conclusions:

• Pre-existing dislocations play a critical role in primary radiation damage production.
• The discovered dislocation-related mechanism is essential for understanding defect formation in irradiated materials.
• Accounting for dislocations is indispensable for assessing and enhancing material irradiation resistance.