Short-range structure of molten CeCl3 and NdCl3 determined by XAFS

The local structures of molten CeCl3 and NdCl3 have been investigated by XAFS at SPring-8 with the K-absorption edges of Ce and Nd. The nearest-neighbour Ln3+–Cl− distances and coordination numbers, n¯LnCl, are found to be 2.81 Å and 6.52 for CeCl3, and 2.73 Å and 6.96 for NdCl3, respectively. The coordination numbers are >6, implying thereby that the local structures around the lighter lanthanide ions are not exactly octahedral, but somewhat distorted. The XAFS technique using the 3rd generation X-ray sources is a powerful tool to elucidate the local structure around the lanthanide ions in the light rare earth compounds.