Calculations of Angular Overlap Parameters for Eu³⁺:Ln₂O₂S(Ln=Lu,Y,Gd,La) Crystal Series

In this paper, for the Eu³⁺:Ln₂O₂S(Ln=Lu,Y,Gd,La) crystal series, the all four angular overlap parameters e_σ、e_π、e_δ、e_φ are considered by Angular Overlap Model(AOM). The results show that the values for e_σ and e_π which have relation with the σ- and π-antibonding effects from the point of view of molecular orbit theory(also for parameters e_σ and e_φ) are decreased with the order of Lu, Y, Gd and La. And σ、π effects are dominant over the δ and φ effects, especially σ effect. Whereas δ and φ effects can be neglected with respect to the σ and π effects in approximate calculations. The magnitude of covalent ability between 4f electrons and ligands in the four crystals is Lu>Y>Gd>La.