Abstract
The crystal structures of CoCl2-, MnCl2-, NiCl2-, and CuCl2-graphite intercalation compounds (GICs) have been studied with single crystal X-ray diffraction methods. The first three intercalates maintain their pristine in-plane CdCl2 structure after intercalation.
The intercalate layers in stage 1 CoCl2-, MnCl2-, NiCl2-GICs stack in an ordered αβTγαβTγ rhombohedral sequence. Additionally, the carbon layers in stage 1 CoCl2-GIC stack in an ordered ABC rhombohedral sequence. For CoCl2-, MnCl2-, and NiCl2,-GICs the intercalate and carbon in-plane lattices exhibit rotational epitaxy. The epitaxy angle is either near 0° or 30°, depending on the intercalate. Current models for rotational epitaxy do not explain the observed rotation angles. The CuCl2 layers have the periodicity of a centred rectangular net and stack, in the stage 1 GIC, in an ordered αβTαβTαβT sequence. The intercalate in stage 1 CuCl2-GIC forms a metrically face centred orthorhombic lattice; however, the symmetry of the intercalate structure is monoclinic. The intercalate interlayer interaction is attenuated by the intervening carbon layers, so that the stacking of the intercalate layers in all of the stage 2 compounds is uncorrelated.