An international collaboration has been formed between Penn State, the Federal University of Rio Grande do Sul, Brazil (UFRGS), and Argonne National Laboratory (ANL), to study point defects in the intermetallic compounds Zr₃Fe, ZrFe₂ and other intermetallics of the Zr-Fe-M system (M=Cr,Co,Ni). We intend to determine the defect configurations and energetics using a combination of experimental and computational techniques. This program will combine three lines of experimental and theoretical research:

a) the study of the irradiation response,of the compounds to electron and ion irradiation at high doses, specially its temperature dependence;

b) the use of nuclear probe techniques - Perturbed Angular Correlation Spectroscopy (PAC), Mössbauer Spectroscopy (MS) and Positron Annihilation Lifetime Spectroscopy (PALS) - to study defects in neutron irradiated compounds;

c) the determination of defect energetics from computational simulations of their crystalline lattices using the embedded-atom method (EAM).

The combined use of the three modes of examination provides a deeper understanding of the defect behavior in those systems than would be possible by performing these tasks individually. The results of the computer simulations are used to identify the stages observed using the nuclear probe methods and associate them with particular defects; and, conversely, the results from nuclear-probe experiments help verify the computer potentials developed for these compounds. Likewise, since the irradiation response of the intermetallics is controlled by defect mobility, the changes in irradiation response with temperature give additional information about the annealing stages of the specific compounds. The results from computer simulations also enable us to design specific in-situ irradiation experiments to test them.

Researchers: A.Paesano, Jr., A.T.Motta, G.L.Catchen, N.Q.Lam, L.Amaral, and S.R.Teixeira.

Funding: National Science Foundation and CNPq- Brazilian National Research Council.