  This work investigates solute transport due to self-interstitial defects and
radiation induced segregation tendencies in dilute ferritic alloys, by
computing the transport coefficients of each system based on ab initio
calculations of binding energies and migration rates. The implementation of the
self-consistent mean field method in the KineCluE code allows to extend the
calculation of transport coefficients to arbitrary interaction ranges, crystal
structures, and diffusion mechanisms. The results show that the diffusivity of
P, Mn, and Cr solute atoms is dominated by the dumbbell mechanism, that of Cu
by vacancies, while the two mechanisms might be in competition for Ni and Si,
despite the fact that the corresponding mixed dumbbells are not stable.
Systematic enrichment at defect sinks is expected for P and Mn solutes due to
dumbbell diffusion, and for Si due mainly to vacancy drag. Vacancy drag is also
responsible for Cu and Ni enrichment below 1085 K. The RIS behavior of Cr is
the outcome of a fine balance between dumbbell enrichment and vacancy
depletion. Therefore, for dilute Cr concentrations global enrichment occurs
below 540 K, and depletion above. This threshold temperature grows with solute
concentration. The findings are in agreement with experimental observations of
RIS and clustering phenomena, and confirm that solute-defect kinetic coupling
plays an important role in the formation of solute clusters in reactor pressure
vessel steels and other alloys.
