Crystal Structures of KCuCl3 and NH4CuCl3

Abstract

The crystal structures of the isomorphous garnet‐red copper salts, KCuCl₃ and NH₄CuCl₃, have been determined. Each compound contains discrete, planar, Cu₂Cl₆⁼ dimers. These dimers are stacked above each other along the crystallographic a axis. The cation exhibits a ninefold coordination. KCuCl₃ is antiferromagnetic below 30°K. Both KCuCl₃ and NH₄CuCl₃ are pleochroic with maximum visible absorption when the electric vector is parallel with the Cu–Cu vector of the dimer.