Melting and Staging in Graphite Intercalated with Cesium

Abstract

The order-disorder transition in Cs-intercalated graphite has been studied using x-ray scattering. In ${\mathrm{C}}_{8}$Cs the Cs layer transforms into a liquidlike phase in which the average Cs-Cs separation is incommensurate with the carbon net. Fundamentally different behavior is observed in a Cs-deficient stage-1 sample where commensurate "lattice-gas" melting occurs. Evidence is presented which shows that in low-stage material, staging is closely related to the melting transition in support of the model of Daumas and H\'erold.