Phase transition in rubidium-intercalated graphite C24Rb

We report the elastic neutron scattering results from C24Rb in the temperature range 10–300 K. Two successive phase transitions occur at 106 and 165 K. At T > 165 K (phase I) the Rb-layers form positional disorder. At 106 K < T < 165 K (phase II) they form an incommensurate triangular lattice modulated by the graphite potential. The principal axis of the Rb lattice is rotated by about 10° relative to the graphite layer. This modulation is described by a static distortion wave (SDW). The Rb-layers have the stacking order with a period of three C-Rb-C sandwiches. At T < 106 K (phase III) the in-plane structure remains unchanged but the stacking order changes into a longer period one.