A mean radius for the first coordination shell in lanthanides

A mean radius R̄ for the first coordination shell of lanthanides in solids is defined in terms of Morrison’s local polarizability model, substituting the shifts of the Slater and spin–orbit parameters by their observed phenomenological values. The results obtained agree within 10% with the measured ion-nearest neighbors’ distances in rare-earth compounds. We used our definition of a mean radius to predict the average Eu3+-nearest ligand’s distance in new luminescent polymer electrolytes. The values found for different concentrations of Eu3+ (2.3–2.7 Å) are compatible with known data for europium.