Single-Crystal X-Ray Scattering Study of Superstructures and Phase Transitions in Graphite-Hno 3 and Graphite-Br 2 Intercalation Compounds

In α-C5n-HNO3 the condensation of the room-temperature liquid-like diffuse ring associated with the disorder-order transition around 250 K is studied and the low-temperature. superstructure is examined. It is found that β-C8n-HNO3 exhibits an in-plane incommensurate order at room temperature. Two types of graphite-Br2 are found. Low-temperature phase transitions in C8Br are observed at T1 ≍ 277 K and T2 ≍ 297 K. The room-temperature structure of C14Br is reexamined. Special attention is given to diffuse scattering and incommensurability.