Molecular Dynamics Study of Irradiation-Induced Defect and Dislocation Evolution in Strained Nickel

TL;DR

This study uses molecular dynamics simulations to explore how mechanical strain influences defect and dislocation behavior in nickel under irradiation, revealing strain-dependent defect dynamics and dislocation saturation.

Contribution

It demonstrates the impact of tensile strain on defect evolution and validates the Kocks-Mecking model for strain-dependent irradiation effects in nickel.

Findings

Tensile strain enhances defect mobility and survival.

Heat spike duration decreases with increasing strain.

Dislocation densities reach a steady saturation value.

Abstract

Molecular dynamics (MD) simulations were performed to investigate the influence of mechanical strain on irradiation-induced defect and dislocation evolution in nickel single crystals subjected to cumulative overlapping 5 keV collision cascades at 300 K. The simulations reveal that tensile strain modifies the dynamics of defect generation and recovery, promoting stress-assisted defect mobility and enhancing defect survival compared to the unstrained case. The heat spike duration and intensity decrease systematically with increasing strain, indicating faster energy dissipation and altered defect recombination behavior under applied stress. Analysis of the dislocation structure shows that Shockley-type partial dislocations dominate the microstructural response, while Hirth and other dislocation types remain comparatively minor. Both the total and Shockley dislocation densities reach a saturation value of $~10^{16}m^{-2}$ , marking the establishment of a steady-state microstructure governed by the balance between dislocation accumulation and recovery. The evolution of the total dislocation density with strain is successfully described by the Kocks-Mecking model, demonstrating its applicability to strain-dependent irradiation effects in metallic systems