Abstract: The energy band structure,density of state and Mulliken charge density of the F₃-center in α-Al₂O₃ are studied by an embedded-cluster model,when H-like wave function is used for F-center.The optical transition model of the color center is also discussed.It found one single energy level and one doubly-degenerate energy level in the fundamental gap of the crystal with F₃-center.There is a new transition from defect energy level to conduction band and the transition energy is 3.54 eV.Comparing with the absorption spectrum of α-Al₂O₃ by high-energy and great flux neutron radiation,shows that 0.356 μm(3.483 eV) experimental absorption peak should be due to the F₃-center.Also,it found the charge density is less in the site of F₃-center than that of Fcenter in α-Al₂O₃ crystal.

Key words: α-Al₂O₃, F₃-center, energy level, transition energy