Positron lifetime calculation in FeCu binary alloy with lattice relaxation

Using the embedded atom type many body potentials for iron and copper, the lattice relaxation around copper impurity atoms in iron has been performed. The stable configuration of atoms around copper and copper vacancy complexes in FeCu alloy was simulated. By introducing a positron into the relaxed lattice of FeCu binary alloy with and without a vacancy, positron lifetimes have been calculated. The positron lifetime in a relaxed FeCu matrix was 119 ps, while in a relaxed Cu-vacancy pair it was 168 ps. The latter, which is shorter than the positron lifetime in a single vacancy, is in good agreement with the experimental lifetime observed in FeCu alloy irradiated with electrons at low temperature.