Electron correlation effects on thef6-manifold of the Eu3+ impurity in Ba2 GdNbO6

Abstract

mThe effects of atomic and molecular electron correlation and Gaunt interaction on the transition energies between the 5D, and 7F1, levels, arising from the 4 f state of the europium ion, have been studied for the ion and for the [EuO6I9-cluster as it is found in the Ba2GdNb06 crystal. The calculations were performed using the MOLFDIR program

The calculation of f-f spectra of lanthanide and actinide ions by the MCDF-CI method

“…As an aside, it is worth noting one further point with regard to internal correlation. It has been found in previous investigations [4,7,8,15] that this type of correlation is important and that of the excitations that can contribute to internal correlation the type nd 2 → nf 2 have the greatest effect on calculated spectra. This is the case for lanthanide ions or the later actinides but in the course of these calculations it was found that for the lighter actinides the (n + 1)p 2 → nf 2 excitations are the most important followed by the nd 2 → nf 2 excitations.…”

“…It was not immediately clear which electrons should be frozen and which should be correlated in the CI calculations. The valence f electrons obviously should be active and earlier calculations have found that the 6s, 6p, 5s, 5p and 5d electrons of the actinide ions (5s, 5p, 4s, 4p and 4d electrons for the lanthanide ions) also need to be correlated to some extent [7,8,15]. In [9] the 4f electrons of U 4+ were correlated and some perturbation calculations have suggested that even lower energy electrons may also need to be correlated [4].…”

“…These calculations include little electron correlation and are of similar accuracy to the present MCDF-EAL results (calculation (i)). Nieupoort and co-workers [14,15] also used an MCDF-CI method much like that applied here but only considered the 5 D 0 → 7 F 1,2 transitions of Eu 3+ . Their most accurate calculation includes all excitations leading to internal correlation and gives results in close agreement with the equivalent calculations (ii) from this paper.…”

“…Their most accurate calculation includes all excitations leading to internal correlation and gives results in close agreement with the equivalent calculations (ii) from this paper. In [14,15] the effects of the environment on the calculated transition energies was included through the inclusion of a lattice of oxygen atoms in the calculation. It was found that the two transition energies considered were reduced by about 300 cm −1 by the presence of the oxygen atoms [14] but that the effects of electron correlation were largely unchanged [15].…”

“…Due to these difficulties, calculations of f-f spectra remain extremely challenging and relatively few investigations have been published in the last few years. The f 2 species Pr 3+ and U 4+ have been studied a number of times [4][5][6][7][8][9][10][11][12][13] but work on more complex systems has been limited to the inclusion of a small amount of electron correlation or a consideration of only the lowest few excited states [10][11][12][13][14][15][16][17].…”