Atomistic study of copper-vacancy clusters in bcc-Fe

Copper-rich precipitates are assumed to be the main cause of hardening and embrittlement of Cu-bearing reactor pressure vessel steels since they act as obstacles to dislocation motion within the grains of polycrystalline bcc-Fe. Multiscale modeling contributes to a better understanding of point-defect-induced formation of these clusters during reactor operation. Rate theory is an efficient tool to simulate the cluster evolution on realistic time and length scales. However, many parameters used in rate theory, such as the diffusion coefficients of mobile species and the free binding energies of clusters, are not very well known from experimental investigations. Atomic-level computer simulations can provide these data.
In the present work the free binding energies are determined for small and medium-sized CunVm clusters in bcc-Fe. The most recent Fe-Cu interatomic potential by Pasianot and Malerba [1] is used. Enthalpy and entropy contributions are calculated using combinations of on-lattice Monte Carlo simulations and off-lattice molecular dynamics calculations.
[1] R. C. Pasianot and L. Malerba, J. Nucl. Mater. 360, 118 (2007).