Charge-Transfer Transitions of RE3+ —O2– Associates in BaF2 Crystal

ABSTRACTLocal-density-functional calculations have been performed to study the electronic structure and charge-transfer transitions of RE3+ —O2–(RE=Eu and Tm) associates in barium fluoride crystal. These systemsare simulated by small clusters which are surrounded by over 2000 point charges. It is found that the presence of oxygen in the lattice strongly influences the optical propertiesof RE3+ ions. The charge transfer transitions of RE3+O2– and RE ions with ligand F— ions derived from the embedded cluster are equal to 5.1 eV and 6.2 eV. The energy gap derived from the HFS model with REOBa2F6 clusters embedded in the crystal is 9.8 eV,which is near the experimental results.