Local structure of molten LaCl3 by K-absorption edge XAFS

Abstract The local structure of molten LaCl 3 was investigated by X-ray absorption fine structure of the La K-edge. The nearest La 3+ –Cl − distance and coordination number were 2.89±0.01 A 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 LaCl 3 is not a simple octahedral coordination (LaCl 6 ) 3− , but 7-fold (LaCl 7 ) 4− and/or 8-fold (LaCl 8 ) 5− complexes. The first La 3+ –La 3+ distance, of which correlation was observed as a weak second peak in the |FT|, was evaluated to be 4.9 A. It suggests that the distorted corner-sharing connection of the complex species is predominant in the melt, in contrast with molten YCl 3 in which the edge-sharing connection of the 6-fold (YCl 6 ) 3− mainly exists.