Ab-initio study of oxygen vacancy stability in bulk and Cerium-doped lutetium oxyorthosilicate

We study from first principles the stability of neutral and charged oxygen vacancies in lutetium oxyorthosilicate, Lu2SiO5, as well as its possible modification due to the presence of Ce3+, as present in commercial scintillators. We show that the neutral oxygen vacancy with the lowest formation energy forms at the oxygen sites within the [SiO4] tetrahedra instead of the interstitial oxygen site bonded exclusively to lutetium atoms. The discrepancy with a previous study is attributed to the quality of the pseudopotential. Support for these results is found by performing a bonding analysis of the oxygen sites, as well as oxygen vacancy calculations in the iso-structural Y2SiO5 compound. In addition, we find that the incorporation of Ce3+ ion does not affect the stability of oxygen vacancies in Lu2SiO5.