Atomistic study of grain boundary sink strength under prolonged electron irradiation

► Prolonged irradiation until steady state is simulated in molecular dynamics simulations. ► Rate theory is revisited with all parameters derived from atomistic simulations. ► The defect accumulations in nanograin Mo from molecular dynamics simulations agree well with the rate theory predictions. ► The grain boundary structures remain unchanged after prolonged irradiation. Grain boundaries (GBs) can act as either sinks or sources of the point defects that are produced in large numbers under irradiation damage. In polycrystalline materials, as the grain size decreases, more of the point defects resulting from irradiation damage annihilate at GBs. It is unknown, however, whether the GB sink efficiency will saturate after prolonged defect annihilation, particularly when the grain size is of nanoscale dimensions. Using a combination of molecular dynamics (MD) simulation and rate theory, the authors show that high-energy GBs in body-centered-cubic (BCC) Mo do not saturate as sinks of point defects. The MD simulations serve to provide direct measurement of defect evolution, and the rate theory serves both to test whether grain boundary sink strength is constant during prolonged defect annihilation, and to extend the MD results to realistic defect production rates.