Local structure of molten LaCl3 by K-absorption edge XAFS

The local structure of molten LaCl3 was investigated by X-ray absorption fine structure of the La K-edge. The nearest La3+- Cl- distance and coordination number were 2.89 +/- 0.01 Angstrom and 7.4 +/- 0.5 from the curve fitting of the first peak in the Fourier transform magnitude \FT\. The coordination number larger than 6 suggests that the local structure of molten LaCl3 is not a simple octahedral coordination (LaCl6)(3-), but 7-fold (LaCl7)(4-) and/or 8-fold (LaCl8)(5-) complexes. The first La3+-La3+ distance, of which correlation was observed as a weak second peak in the \FT\, was evaluated to be 4.9 Angstrom. It suggests that the distorted corner-sharing connection of the complex species is predominant in the melt, in contrast with molten YCl3 in which the edge-sharing connection of the 6-fold (YCl6)(3-) mainly exists. (C) 2002 Elsevier Science B.V. All rights reserved.