A study was made of the structures and energies of vacancy-Cu clusters in α-Fe, which provided fundamental information for understanding the mechanism of neutron-irradiation embrittlement of nuclear reactor pressure vessel materials. Extensive molecular dynamics and Monte Carlo computer simulations with the use of the embedded atom method potential for the Fe-Cu system were performed in order to obtain energy-minimum structures of vacancy-Cu clusters of various sizes in a α-Fe matrix. It was found that, in general, a vacancy-Cu cluster consisted of a vacancy cluster buried at the center of a Cu shell. The formation energies for the vacancy-Cu clusters were calculated from the MD results, and an equation was developed which described the formation energy as a function of the numbers of vacancies and Cu atoms. It was found that the number of Cu atoms on the surface of the vacancy cluster played an important role in determining the formation energy of the vacancy-Cu clusters. The binding energies of a vacancy and a Cu atom to the vacancy-Cu clusters were also calculated. It was found that the interaction between vacancies and Cu atoms enhanced the binding of the vacancy-Cu clusters.

Structures and Energies of Vacancy-Cu Clusters in α-Fe. A.Takahashi, N.Soneda, S.Ishino, G.Yagawa: Physical Review B, 2003, 67[2], 024104 (9pp)