CALCULATIONS OF DEFECT PROPERTIES IMPORTANT IN PHOTOREFRACTIVE SR0.6BA0.4NB2O6

An interatomic potential model for Sr0.6Ba0.4Nb2O6 (SBN) has been developed by transfer of potentials from similar oxide crystals. The model has been used to examine defect properties of SBN important in the photorefractive effect. Our calculations indicate randomness on the Ba/Sr sublattice, and the possibility of O- and Nb4+ small polarons when extra carriers are present. A self-compensation reaction is found to be a preferred incorporation model for tetravalent and trivalent impurities giving substitution on Nb and Ba/Sr sites. Our calculations indicate that Ce3+, Fe2+, and Mn2+ substituted on Ba/Sr sites can act as a donor to facilitate the photorefractive effect in SBN.