Abstract
The superposition model is applied to the calculation of intrinsic parameters Ā 2(R), Ā4(R) and Ā6( R) for each europium-ligand distance in LaCl3, LaAlO3 , La2O3 and La2O2S. These parameters allow one to draw conclusions regarding the covalency of these compounds and, in some cases, to characterize the europium-ligand bonding. On the other hand, for weakly covalent compounds, the σ* parameters may be determined by the angular overlap model