Influence of foreign atoms on the diffusion of oxygen in bcc Fe

Iron-based ferritic alloys are widely used in industrial applications. They contain varying concentrations of foreign atoms or solutes, most of which are purposely included in order to improve the mechanical properties, the corrosion and radiation resistance as well as the high-temperature stability. The diffusion of the solutes plays a crucial role in determining all these properties during fabrication and processing, and also influences the behavior of the materials in the various applications. In many cases the diffusion proceeds via bcc lattice sites by means of intrinsic point defects, i.e. vacancies and self-interstitial atoms, and in some cases via interstitial sites. Solute diffusion determines the micro- and nanostructure obtained after heat treatments, and the detailed knowledge of the atomistic diffusion mechanisms is necessary to obtain the desired properties. Moreover, micro- and nanostructure evolution under irradiation is controlled by atomic diffusion.
In this research project (started in September 2016) the diffusion of foreign atoms in bcc Fe shall be investigated by first-principle methods and kinetic Monte Carlo simulations. The focus of the present work is on the diffusion of oxygen under the influence of other foreign atoms such as Al, Cr, Ti, and Y. Oxygen plays an important role in the formation and evolution of a high dispersion of nanometer-size particles containing Y, Ti, and O in ODS steels which are considered as promising candidates for structural materials of future fusion and fission reactors [1]. The presence of foreign atoms and intrinsic point defects modifies the original migration path of oxygen [2-4]. Using DFT calculations the binding energy between oxygen and a foreign atom for different neighbor distances and the modified migration barriers, i.e. for the O jump between the first and the second neighbor of a foreign atom, etc are calculated.
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