Local structure of molten LaCl3 analyzed by X-ray diffraction and La–LIII absorption-edge XAFS technique

From the radial distribution analysis of X-ray diffraction, the nearest neighbor La–Cl distance and coordination number of Cl around La in molten LaCl3 were estimated to be about 0.28 nm and nearly equal to 6, respectively. On the other hand, according to the XAFS measurements, the coordination number of Cl around La was evaluated at about 7. As a result, the local structure of molten LaCl3 was thought to be described as an octahedral-like coordination scheme where La was surrounded by about six or seven Cl's. This finding led to the formation of octahedral complex ion, LaCl63−, which was in agreement with results of Raman spectroscopy by other authors. The La–La distance was evaluated at about 0.5 nm from the position of a weak and broad second peak in the correlation function g(r), suggesting that a distorted corner-sharing connection of two octahedral complex species was predominant in the melt.