Crystal Structures of Anhydrous Rare-Earth Chlorides

Abstract

The crystal structures at 298°K of LaCl₃, NdCl₃, EuCl₃, and GdCl₃ have been refined by full‐matrix least‐squares methods using three‐dimensional $\mathrm{Mo}\mathrm{K\alpha }$ intensity data. These isomorphous compounds belong to the ${\mathrm{UCl}}_3{\text{‐P6}}_3\mathrm{\hspace{0.17em}/\hspace{0.17em}m}$ structure type; metal atoms occupy symmetry sites at $(\frac{1}{3},\frac{2}{3},\frac{1}{4})$ and chloride ions lie on mirror sites at $\mathrm{(x,\; y,}\frac{1}{4})$ with $\text{x≅0.39}$ and $\text{y≅0.30}$ . Standard deviations of the interatomic separations do not exceed 1 part in 1000.