Structural study of stage-1 cesium graphite at high temperatures

New x-ray-diffraction results on the high-temperature structure of state-1 Cs graphite as a function of sample temperature and Cs-vapor pressure are presented. It is shown that the dominant factor in determining the high-temperature structure is the concentration of Cs atoms. An order-disorder transition occurs when the saturated compound ${\mathrm{C}}_8$Cs decomposes. The decomposition occurs in two steps. The sample first transforms from the 300-K ordered phase with $\alpha \beta \gamma$ stacking to an unstable ordered phase with $\alpha \beta$ stacking. Then the sample undergoes an order-disorder transition to a phase with "liquidlike" planar structure. Also presented is evidence for the existence of an $\alpha \beta \gamma \delta$ stacking sequence in stage-1 Cs graphite at 300 K.