Dynamical stability of radiation-induced C15 clusters in iron

TL;DR

This study uses molecular dynamics with a new potential to investigate the formation, stability, and evolution of C15 interstitial clusters in iron under irradiation, revealing their significant role in defect dynamics and loop formation.

Contribution

It introduces a new bond-order potential for simulating radiation damage and provides detailed insights into the stability and growth of C15 clusters in irradiated iron.

Findings

C15 clusters constitute 5-20% of initial interstitials in cascades.

C15 clusters are highly stable and grow by absorbing interstitials during irradiation.

Growth of C15 clusters leads to collapse into dislocation loops, mainly 1/2<111> loops.

Abstract

Density functional theory predicts clusters in the form of the C15 Laves phase to be the most stable cluster of self-interstitials in iron at small sizes. The C15 clusters can form as a result of irradiation, but their prevalence and survival in harsh irradiation conditions have not been thoroughly studied. Using a new bond-order potential optimised for molecular dynamics simulations of radiation damage, we explore the dynamical stability of the C15 clusters in iron under irradiation conditions. We find that small C15 clusters make up 5-20% of the interstitial clusters formed directly in cascades. In continuous irradiation, C15 clusters are frequently formed, after which they remain highly stable and grow by absorbing nearby single interstitial atoms. Growth of C15 clusters ultimately leads to collapse into dislocation loops, most frequently into 1/2<111> loops and only rarely collapsing into <100> loops at low temperatures. The population, size, and collapse of C15 clusters during continuous irradiation correlates well with their formation energies relative to dislocation loops calculated at zero Kelvin.