The effect of divacancies on positron annihilation in Cu

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Abstract
The effect of divacancies has been observed on the temperature dependence of gamma - gamma angular correlation of positron annihilation in copper. The peak counting rates of the angular correlation are higher at temperatures near the melting point than those predicted by the trapping model assuming that only single vacancies exist. Numerically analysing the results by the trapping model including divacancies, the formation energy of a single vacancy and the binding energy of a divacancy were estimated to be 1.28+or-0.06 eV and 0.3+or-0.1 eV, respectively.