  The results of positron annihilation lifetime spectroscopy measurements on
undoped, electron irradiated, and Nb doped SrTiO3 single crystals are reported.
Perfect lattice and vacancy defect positron lifetimes were calculated using two
different first-principles schemes. The Sr vacancy defect related positron
lifetime was obtained from measurements on Nb doped, electron irradiated, and
vacuum annealed samples. Undoped crystals showed a defect lifetime component
dominated by trapping to Ti vacancy related defects.
