Electronic structure of an oxygen vacancy in lithium niobate

Abstract

We report the results of electronic-structure calculations on an oxygen vacancy in lithium niobate using the scattered-wave X\ensuremath{\alpha} cluster method. This defect has been tentatively identified in reduced lithium niobate by correlated optical-absorption and electron-paramagnetic-resonance studies, where it is the dominant optically active defect. However, such a strong absorption is rather surprising based on defect-chemistry studies, where an oxygen vacancy would at best be a minority defect in such a sample. We find that an oxygen vacancy would be characterized by electron(s) which are well localized on the niobium atom(s) adjacent to the vacancy site. As a consequence, the oscillator strength for the corresponding bound-to-bound transition may be too small to account for the observed optical absorption.