Formation, migration, and clustering of delocalized vacancies and interstitials at a solid-state semicoherent interface

Abstract

Atomistic simulations are used to study the formation, migration, and clustering of delocalized vacancies and interstitials at a model fcc-bcc semicoherent interface formed by adjacent layers of Cu and Nb. These defects migrate between interfacial trapping sites through a multi-step mechanism that may be described using dislocation mechanics. Similar mechanisms operate in the formation, migration, and dissociation of interfacial point defect clusters. Effective migration rates may be computed using the harmonic approximation of transition state theory with a temperature dependent prefactor. Our results demonstrate that delocalized vacancies and interstitials at some interfaces may be viewed as genuine defects, albeit governed by mechanisms of higher complexity than conventional point defects in crystalline solids.2

Non-coherent Cu grain boundaries driven by continuous vacancy loading

“…Molecular dynamics (MD) may be used to simulate small numbers of such migration events at elevated temperatures [36][37][38]. However, the simulation times required to model a continuous vacancy influx by direct MD are prohibitively long, especially at low homologous temperatures.…”

Stable Storage of Helium in Nanoscale Platelets at Semicoherent Interfaces

“…At room temperature, this interval is sufficient not only for every implanted atom to reach an MDI before the next one arrives, but also for the free volume at the MDI to equilibrate through interfacial vacancy diffusion [29,30]. Therefore, to simulate He trapping we adopt an iterative approach-detailed in supplement 2-for adding He atoms to the interface while allowing the number of vacancies in it to adjust freely.…”

Defect Distributions and Transport in Nanocomposites: A Theoretical Perspective

“…That said, there are certainly a number of other factors that influence radiation damage in nanomaterials, including the mechanisms for recombination, [21] the energetics of the interfaces themselves, [17] and the role of trap states at the interfaces. [22][23][24] A comprehensive model of radiation damage evolution in nanomaterials would need to account for all of these factors. The simple model presented here, however, suggests that the relative properties of point defects in the different phases of a nanocomposite are of great importance.…”