Grain-boundary source/sink behavior for point defects: An atomistic simulation study

Abstract

Abstract The grain-boundary source and sink strengths for both vacancies and self-interstitials have been determined for columnar nanocrystalline structures of Mo using molecular-dynamics simulation. The microstructures, which are initialized to contain either an over-saturation or under-saturation of one particular point defect species (either vacancies or self-interstitials), are subjected to isothermal annealing at high homologous temperatures (T > 0.75Tm) while the point-defect concentrations are monitored throughout. We clearly observe an exponential approach of the point-defect concentrations to equilibrium, in agreement with classical rate theory. These observed approaches to equilibrium yield grain-boundary source/sink strengths that correlate with analytical solutions that depend solely on the grain size. Finally, we find that grain boundary sinks have an approximately equal affinity, or bias, to vacancies and self-interstitials.