Role of point-defect sinks on irradiation-induced compositional patterning in model binary alloys

The dynamical competition between the chemical mixing forced during energetic particle irradiation and thermally activated decomposition can lead to the stabilization of self-organized steady states in alloy systems comprised of immiscible elements. Continuum modeling and atomistic simulations predicted the stabilization of steady-state nanoscale compositional patterns for a well-defined range of ballistic mixing frequencies normalized by the irradiation-enhanced thermal atomic jump frequencies. Irradiation-induced compositional patterning has now indeed been observed experimentally, but a quantitative comparison has been lacking because models and simulations have relied on a simplified treatment with a fixed point-defect concentration. We overcome here this limitation by using a kinetic Monte Carlo code that includes the production, recombination, and elimination of point defects at sinks, as well as the chemical mixing forced by ballistic replacements. By varying the sink density and its efficiency, the temperature range of stabilization of steady-state compositional patterns is investigated in model binary alloys for point-defect regimes dominated by either recombination or elimination on sinks. We find that in the sink regime, compositional patterning can be extended to remarkably high temperatures. The results are discussed by analyzing the relative diffusivities of A and B species, and their dependencies on temperature.