Clusters containing Ln2+ ions in doped crystals of inorganic compounds have been studied by analytical Hartree–Fock wave functions for the excited 4fN–15d configurations. Two-center overlap integrals, Ln2+–ligand, of the type \(\langle ns|{4f}^{N-1}\rangle\) , \({\langle np|{4f}^{N-1}\rangle }_{\sigma }\) , \({\langle np|{4f}^{N-1}\rangle }_{\pi }\) , where n = 2 or 3, have been computed for Ln2+: Y3Al5O12, Ln2+: MIIF2, LnS, and Ln2+:MICl, with Ln = Nd, Sm, Eu, Dy, Tm, and Yb; two-center overlap integrals \(\langle 2s|5d\rangle ,\) \({\langle 2p|5d\rangle }_{\sigma },\) and \({\langle 2p|5d\rangle }_{\pi }\) have been also evaluated. Two-electron contributions to spectroscopic polarizabilities have been determined by differences in the radial expectation values \({\langle {r}^{2}\rangle }_{5d}-{\langle {r}^{2}\rangle }_{4f}\) , for Ln2+ ions from two different sources have been determined and discussed. The novelty of the study comprises the first and explicit use of Hartree–Fock wave functions for Ln2+ ions in the 4fN–15d configurations applied to covalency effects on the polarization energies.
