Papers by Keyword: Copper Cluster

Abstract: Defect studies of neutron-irradiated Cr-Mo-V (VVER-440) type reactor pressure vessel steels were performed in the present work. The steels were irradiated in the nuclear power plant reactor under the conditions of a regular operation. Characterization of the irradiation induced defects was performed by two complementary techniques of positron annihilation spectroscopy: (i) positron lifetime spectroscopy was used for identification of defects and determination of defect densities, (ii) coincidence Doppler broadening was employed for investigation of Cu atom aggregates. Long range diffusion of Cu atoms is assisted by the irradiation induced vacancies. The solute Cu atoms form small clusters in the irradiated steels. Subsequent isochronal annealing of the irradiated steel leads to vacancy assisted clustering of Cu atoms and formation of small precipitates. The Cu clusters exhibit maximum diameter at 400oC. Above this temperature the clusters dissolve again in the matrix.

Abstract: The Monte Carlo(MC) and Embedded-Atoms Method(EAM) potential are employed to investigate the structures and binding energies of copper clusters. Three results are obtained: first, the copper clusters are formed by gradually increasing atoms to icosahedral surface when the temperature is 300K and the number of atoms is from 2 to 70; second, the higher the symmetries are, the more stable the structures of copper clusters are; third, copper clusters tend to be stereo construction but not planer construction when the number of atoms is less. The structure of Cu147 is three-fly-icosahedron when the system of 147 atoms reached equilibrium at 300K. And at 700K, all 500 atoms form clusters in gas phase.