Unfaulting mechanism of trapped self-interstitial atom clusters in bcc Fe: A kinetic study based on the potential energy landscape

Abstract

We report on the complete unfaulting mechanism of a trapped self-interstitial atom cluster in the form of a nonparallel configuration (NPC), investigated using the autonomous basin climbing (ABC) method. A detailed set of transition state atomic trajectories in the unfaulting process from the trapped to the mobile glide $⟨111⟩$ configuration and the corresponding potential energy landscape were identified. The breaking of the initial ring structure of the three trimers on (111) planes followed by the rotation of the $⟨111⟩$ crowdion in the NPC are the main rate limiting processes of the unfaulting mechanism. The effective activation barrier in the transition from the NPC to the glide $⟨111⟩$ configuration was calculated by combining the ABC and kinetic Monte Carlo methods and was further benchmarked against molecular dynamics (MD) simulations. The effective activation barrier was found as 0.82 eV; smaller than its previously reported value of 1.68 eV. The ABC method was confirmed to be more efficient than MD, especially for the defect structure evolution processes associated with high barriers and at low temperatures.