文摘
Some features of the interaction of the 4fN configuration of tripositive lanthanide ions (Ln3+) with excited configurations have been investigated. The calculated barycenter energies of the same parity 4fN鈥?6p, 4fN+15p5, and 4fN鈥?5f configurations for Ln3+, relative to those of 4fN, are fitted well by exponential functions. The 4fN barycenter energies of Ln3+ in Y3Al5O12/Ln3+ lie in the band gap, with the exceptions of Tb3+ and Yb3+, where they are situated in the conduction and valence bands, respectively. The configuration interaction parameters 伪, 尾, and 纬, which are fitted in the usual phenomenological Hamiltonian to calculate the crystal field energies of Ln3+, exhibit quite variable magnitudes in the literature due to incomplete energy level data sets, energy level misassignments and fitting errors. For LaCl3/Ln3+, 83% of the variation of 伪 and 50% of that for 尾 can be explained by the change in the difference in barycenter energy with the predominant interacting configuration. The parameter 纬 is strongly correlated with the Slater parameter F2 and is not well-determined in most calculations. The values of the electrostatically correlated spin鈥搊ther orbit parameter P2 vary smoothly across the Ln3+ series with the barycenter difference between the 4fN and 4fN鈥?5f configurations. Calculations of the Pk (k = 2, 4, and 6) values for Pr3+ show that 4f 鈫?nf excitations only account for 鈭?5% of the value of P2 for LaCl3/Pr3+ and 35% of that in Y3Al5O12/Pr3+. The role of the ligand is therefore important in determining the value, and a discussion is included of the present state of configuration-interaction-assisted crystal field calculations. Further progress cannot be made in the above areas until more reliable and complete energy level data sets are available for the Ln3+ series of ions in crystals.