Atomic diffusion in pure α-Fe and Fe-1at%Cu crystals via vacancies was investigated by molecular-dynamics computer simulation. In order to generate a large statistical set, modelling was performed at 1000 to 1800K. The migration energy and pre-exponential factors in diffusion coefficients of Cu and Fe atoms were estimated and compared with the results of a 5-frequency model, using different approaches for the frequencies, and Monte Carlo studies, where the energy barriers were obtained by molecular statics. It was concluded that the five-frequency model was valid. The vacancy-copper atom cross-diffusion coefficient was estimated by both molecular-dynamics and Monte Carlo methods and was concluded to be negative over the entire temperature range studied,

indicating that under irradiation conditions Cu atoms migrate in the direction opposite to the vacancy flux. It was observed that, at above 1500K, about 0.5% of the vacancy jumps were double jumps, when 2 atoms move simultaneously in a <111> direction towards the vacancy.

Simulation of Copper Atom Diffusion via the Vacancy Mechanism in a Dilute Fe-Cu Alloy. A.C.Arokiam, A.V.Barashev, D.J.Bacon, Y.N.Osetsky: Physical Review B, 2005, 71[17], 174205 (10pp)