The formation energies of a vacancy in pure Cu, Cu-Si, Cu-Ga and Cu- gamma Mn solid solutions by positron annihilation

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Abstract
The temperature dependence of peak counting rates of gamma - gamma angular correlation curves of positron annihilation has been measured for pure Cu, Cu-3.9at%Si, Cu-7.8at%Si, Cu-4.6at%Ga, Cu-8.3at%Ga, Cu-15.0 at %Ga and Cu-8.0at.%Mn. All the measurements were performed at thermal equilibrium from temperatures above the melting points to room temperature. Measured data were analyzed according to the positron trapping model and the values of the apparent formation energy of a single vacancy were found to be 1.21+or-0.02 eV, 1.13+or-0.02 eV, 0.92+or-0.02 eV, 1.10+or-0.02 eV, 1.02+or-0.02 eV, 0.88+or-0.02 eV and 1.19+or-0.02 eV, respectively. Some differences among thermal equilibrium data are considered and relations between apparent formation energies of a vacancy and melting temperatures are discussed. Evidence that the apparent formation energies of copper solid solutions are approximately proportional to the electrons per atom ratio was found.