Interpretation of the optical absorption spectrum and of the paramagnetic susceptibility of neodymium trifluoride

Abstract

The absorption spectrum of single crystal NdF3 of tysonite structure was recorded at liquid helium temperature up to 33 800 cm−1. 127 Stark levels were obtained and fitted to a mean square deviation of 24 cm−1 with a Hamiltonian involving 12 free atom parameters and four D3h crystal field parameters. The fit was improved to a mean square deviation of 14 cm−1 by adding five supplementary crystal field parameters to approach the real C2 symmetry of the site. The paramagnetic susceptibilities parallel and perpendicular to the trigonal axis in the structure were measured from 4.2 to 1100 K and compared with the values derived from the wave vectors of the 18 lowest Kramers doublets through the application of the Van Vleck formula. An overall good agreement was found. The material is anisotropic, χ∥ being larger than χ⊥.

Lanthanide tetrad effect in the Ln3+ ionic radii and refined spin-pairing energy theory

“…Such a difference in E 1 or E 3 between the gaseous free ion and trifluoride is quite small in contrast to the considerable difference between trifluoride and sesquioxide. This decreasing se quence of Racah parameters and the relative magnitudes of the consecutive differences seem to be consistent with the nephelauxetic effect pro posed from spectroscopic data (Jorgensen 1963(Jorgensen , 1979Wong et al, 1963;Caro et al, 1981). This is further clarified in the next section by applying the RSPET formulation of eq.…”

“…In particular, E' is known to correlate with the parameter y, which is one of the additional parameters «, 8, and y relating to the configuration interaction (Rajnak, 1965;Goldschmidt, 1978). Therefore, E' and y cannot be determined uniquely (Carnall et al, 1968a;Caro et al, 1981). In con trast, the,value of the spin-orbit coupling con stant was relatively well defined in the early stage of the iterative fitting procedure for the spec troscopic data of each Ln3" aquo ion (Carnall et al, 1968a).…”

“…Procedure (II) did not improve the result by the procedure (I). The fitting by procedure (III) was made by assuming C,,=4.1 x 10-4 J/mol, based on the zl (4f(Nd) value of 21 cm-' from spectroscopic C4f(NdF3) and (4f(NdO1.5) values (Caro et al, 1981). This assumption means that the spin-orbit interaction parameters for the gaseous free Ln3+ ions are ap proximately equal to those for LnF3.…”

The original examples of lanthanide tetrad effect in solvent extraction: A new interpretation compatible with recent progress in REE geochemistry.

“…(4), Racah (E 1 and E 3 ) parameters for 4f electron repulsion in Ln 3+ ions are not exactly the same between them, although the differences are usually only of percent order or less (Reisfeld and Jørgensen, 1977;Jørgensen, 1979;Caro et al, 1981). The Racah (E 1 and E 3 ) parameters decrease slightly from the gaseous free ion values as a function of the anionic ligands involved in different Ln(III) complexes (Reisfeld and Jørgensen, 1977; Peppard et al (1969) were digitized by means of a largescale magnification in Masuda (1995).…”

Thermochemical parameters for solution of lanthanide(III) ethylsulphate and trichloride hydrate series: Tetrad effects and hydration change in aqua Ln3+ ion series.

“…This is well known as the nephelauxetic series in the ligand field theory for Ln(III) complexes (Jt rgensen, 1979;Caro et al, 1981). LnF3 is a representative compound having largest Racah parameters close to those of free Ln3+ ion, whereas Ln015 is an other representative one characterized by small est Racah parameters.…”