Small-Angle Twist Grain Boundaries as Sinks for Point Defects.

Area of Science:

• Materials Science
• Solid State Physics
• Radiation Damage

Background:

• Grain boundaries (GBs) are crucial defect sinks in irradiated materials.
• Radiation-induced changes in GB atomic structure and chemistry affect their sink efficiency.
• Limited understanding exists for twist GBs' defect absorption mechanisms and saturation behavior.

Purpose of the Study:

• Investigate defect accommodation mechanisms in twist grain boundaries.
• Determine the evolution of twist GBs under irradiation conditions.
• Assess the saturation limits of twist GBs as defect sinks.

Main Methods:

• Combined molecular dynamics and grand canonical Monte Carlo simulations.
• Utilized Silicon Carbide (SiC) with {001} and {111} twist GBs as model systems.
• Analyzed defect diffusion, accumulation, and structural evolution at GBs.

Main Results:

• Defect diffusion along twist GBs in SiC is slow, leading to accumulation.
• Point defects accumulate at twist GBs, driving structural and chemical evolution.
• Screw dislocations within twist GBs absorb interstitials by forming climbable mixed dislocation segments.
• Twist GBs accommodate high interstitial densities without structural degradation, irrespective of flux.

Conclusions:

• Twist GBs evolve structurally and chemically to accommodate non-equilibrium defect concentrations.
• The formation of mixed dislocations is a key mechanism for interstitial absorption at twist GBs.
• Twist GBs exhibit resilience and high capacity for defect absorption under irradiation.