Structure and properties of oxygen centers in CaF2 crystals from ab initio embedded cluster calculations

Abstract

We present the results of ab initio calculations of several intrinsic and oxygen-containing defects in CaF2 including an F center, a substitutional O- ion, an O2--vacancy dipole, and F-A(O2-) and F-2A(+)(O2-) centers. The calculations have been performed using a hybrid density functional and an embedded cluster method. The calculated optical absorption (OA) spectra and magnetic properties are in a very good agreement with available experimental data. It is suggested that isolated substitutional O- ions induce an OA band in the vacuum ultraviolet region at about 7 eV. The nature of the OA bands associated with O2--vacancy dipoles and other, more complex, defects is clarified and corresponding luminescence mechanisms are discussed.