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 2300-3300cm-1, which became 4600cm-1 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 Γ5 (22A) and the next emission from Γ5 (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.