Ab initio calculations on the local structure and the 4f-5d absorption and emission spectra of Ce3+-doped YAG

The 4f¿5d absorption and emission spectra of Ce3+-doped YAG (Y3Al5O12) are simulated with a quantum chemical ab initio embedded cluster approach applied to Ce3+ substitutional defects of D2 local symmetry. The only empirical information used is the structure of the pure host. The simulated absorption spectrum is calculated with overestimations of 2300–, which became in the luminescence. The three 4f¿5d observed absorptions were assigned and the energies of the two remaining ones, which are hidden by the absorption of the pure host, were predicted. The lowest 5d¿4f emission was found to take place from G5 (22A) and the next emission from G5 (32B3). Good absorption and emission band shapes and relative intensities are obtained. A large underestimation of the Stokes shift is found, which suggests an underestimation of the relaxation on the emitting state