Structure and energetics of nanoclusters in bcc-Fe containing vacancies, Cu, and Ni.


Structure and energetics of nanoclusters in bcc-Fe containing vacancies, Cu, and Ni.

Al-Motasem, A. T.; Posselt, M.; Bergner, F.; Birkenheuer, U.

Reactor pressure vessel (RPV) steels consist of polycrystalline bcc-Fe containing Cu, Ni and other foreign atoms. The continuous irradiation by fast neutrons leads to supersaturation of vacancies and self-interstitials and enhances the diffusion of Cu and Ni which occurs via the vacancy mechanism. These processes favor the formation of nanoclusters consisting of vacancies, Cu and Ni. The interaction of dislocations with these precipitates is considered to be the main cause of hardening and embrittlement of the RPV steels. In order to model the evolution of the precipitates under irradiation by rate theory or object kinetic Monte Carlo simulations, the energetics and thermodynamics of the clusters must be known. These data are hardly obtainable by experiments, however, they can be provided by atomic-level computer simulations. In the present work a combination of on-lattice simulated annealing based on Metropolis Monte Carlo simulations and off-lattice relaxation by Molecular Dynamics calculations is employed to determine structure and energetics of the nanoclusters. In particular the influence of Ni on the formation of clusters containing Cu and/or vacancies is investigated. The atomistic simulations show that ternary clusters exhibit a shell structure with a core consisting of vacancies followed by a shell of Cu and an outer shell of Ni. Binary vacancy-Cu and Ni-Cu clusters show a similar shell structure, whereas the atomic configuration of vacancy-Ni agglomerates is completely different. For further application in rate theory and object kinetic Monte Carlo simulations compact and physically-based fit formulae are derived from the atomistic data for the total and the monomer binding energy.

Keywords: Fe-Cu-Ni; defects; Metropolis Monte Carlo and Molecular Dynamics

  • Lecture (Conference)
    E-MRS 2011 SPRING MEETING IUMRS ICAM 2011 & E-MRS/MRS BILATERAL CONFERENCE on ENERGY, 09.-13.05.2011, Nice, France

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Publ.-Id: 15662