Phase transitions at room temperature in graphite intercalation compounds of Re 2 O 7

In graphite intercalation compounds of Re2O7 ('stage 3' compound) Re is arranged in slightly distorted ReO4 tetrahedra. The in-plane lattice of the intercalated phase was investigated by X-ray diffraction (monochromatic Laue technique). Stacking disorder and domain twinning produce very complex diffraction patterns. The intercalate changes its in-plane structure within 200 days from a liquid to a distorted crystalline and lastly to a solid 2d-crystalline phase with lattice constants a = 764 pm, b = 652 pm, and gamma = 100 degrees. Diffuse diffraction phenomena are interpreted by a one-dimensional order model.