Melting points of lanthanide trichlorides

Summary

The melting temperatures and absolute values of melting enthalpies of lanthanide trichlorides decrease from LaCl₃to TbCl₃and then increase to LuCl₃. The preceding decrease cannot be explained by the lattice energies of the trichlorides, since they increase continuously from the lanthanum to the lutetium compounds. However, it may be attributed to the structural features of the liquid state. The liquids near the melting points consist of clusters of complex units, which become larger with decreasing radii of the metal ions. To prove this assumption additional quantitative investigations are necessary.