Ab-initio study on the electronic structures of LiLuF4 crystal containing F and F2 color centers

The electronic structures of LiLuF4 crystals containing F and F2 color center with the lattice structure optimized are studied based on the density functional theory (DFT). The lattice is optimized by using ABINIT package. The calculations by using DV-X alpha(α) indicate that both the F and F2 centers create donor electronic density peak within the forbidden band of the perfect crystal. The electronic transition energies from the donor level to the bottom of the conduction band are 3.95 and 2.39 eV, corresponding to the 315 and 520 nm absorption bands, respectively. It is concluded that the 315 and 520 nm absorption bands are originated from the F center and F2 centers, respectively in LiLuF4 crystal.