Studio perturbativo di cluster delle proprietà elettroniche dello scintillatore Lu2SiO5 dopato con Ce utilizzato nel medical imaging

The purpose of this thesis is to study the optical properties of cerium-doped lutetium oxyorthosilicate, Lu2SiO5:Ce (LSO:Ce), by computing the excitation energies (Eexc) of the first excited states. This was accomplished by using two different computational ap- proaches in parallel: in the first one the Eexc of the periodic LSO:Ce is studied by means of the ∆-SCF approach, using the ab initio CRYSTAL code based on Hartree-Fock(HF) and DFT methods; in the meanwhile a cluster structure is cut out from the periodic system and studied, firstly at DFT level in order to assess the quality of the cluster and later using the today’s highest level of theory for studying the excitation, SA-CASSCF and CASPT2, employing the post-HF code, MOLPRO.