@article{oai:nagoya.repo.nii.ac.jp:00007705,
 author = {KAWABE, Iwao and TAKAHASHI, Takafumi and TANAKA, Kazuya and OHTA, Atsuyuki},
 journal = {The Journal of Earth and Planetary Sciences, Nagoya University},
 month = {},
 note = {Light REE^3+(aq) is a mixture of two distinguishable species of nonahydrate and octahydrate in equilibrium with respect the hydration change reaction that [REE(H_2O_8]^3+(aq)+H_2O(I)=[REE(H_2O)_9]^3+(aq), and the apparent hydration number of light REE^3+(aq) is changing across the series. Here is discussed nephelauxetic effects of the two REE^3+(aq) series from ΔH^0_γ data for the hydration change reaction and the tetrad effect variations of their hydration enthalpies (ΔH_hyd.) and REE-OH_2 distances. The ΔH^0_γ data combined with those data for solution of REE(ES)_3・9(H_2O) with ES = C_2H_5SO_4^- reported previously, suggest that Racah (E^1 and E^3) parameters for light REE^3+ like Nd^3+ decrease in the following order:[REE(H_2O)_9]^3+(aq)>REE(ES)_3・9(H_2O)> [REE(H_2O)_8]^3+(aq). The average REE^3+-OH_2 distance also decreases in this order. Hence this is a nephelauxetic series that Racah parameters are reduced with decreasing REE^3+-OH_2 distance. The Racah parameters for [REE(H_2O)_9]^3+(aq) series are fairly large and comparable with those of gaseous free REE^3+. No significant tetrad effect is expected in its series variation of (-ΔH_hyd.). By contrast, [REE(H_2O)8]^3+(aq) series has significantly smaller Racah parameters than gaseous free REE^3+, and a convex tetrad effect is expected in the series variation of (-ΔH_hyd.). Since (-ΔH_hyd.). of [REE(H_2O_8)]^3+(aq) in heavy REE series is fitted to a linear function of the reciprocal of observed REE-OH_2 disrance in REECl_3 solution, this relation has been extended to light REE series, and a similar relation for [REE(H_2O)_9]^3+(aq) in light REE series has also been determined from our thermodynamic mixture model and observed REE-OH_2 distances in REECL_3 (REE=La, Pr and Nd) solutions. The reciprocal of REE-OH_2 distance in [REE(H_2O)_8]^3+(aq), when plotted against the atomic number of REE, indicates a small convex tetrad effect whereas such an effect is absent in [REE(H_2O)_9]^3+(aq) , in accordance with their nephelauxetic effects. Interestingly, (-ΔH_hyd.) of [REE(H_2O)_9]^3+(aq) satisfies a linear function of 1/(REE-OH_2), and at the same time, the series variations of both (-ΔH_hyd.) and 1/(REE-OH_2) exhibit small convex tetrad effects when plotted against the atomic number of REE. This is analogous to the relationship between the lattice enthalpy of REEO_1.5(cubic) and REE-O distance. The property of (-ΔH_hyd.) and the lattice enthalpy of REEO_1.5 can be understood from the viewpoints: i) the existence of REE(III) cluster with the equilibrium configuration having the minimum energy by itself, and ii) the classical limit in quantum-chemical energetics where Planck’s constant (h) equals zero. It is emphatically noted that the observed tetrad effects and RSPET can complement the classical ion model with a tactic by which internal structures of the real REE^3+ ions are legitimately introduced into our thermodynamic discussion., 国立情報学研究所で電子化したコンテンツを使用している。},
 pages = {51--71},
 title = {Hydration change reaction of light REE^3+(aq) series-II:Contrasting nephelauxetic effects between hydrated [REE(H_2O)_9]^3+ and [REE(H_2O)_8]^3+ series and the tetrad effects in their hydration enthalpies and REE-OH_2 distances},
 volume = {53},
 year = {2006}
}