AN IDEAL STAGE TRANSITION MODEL OF POTASSIUM GRAPHITE INTERCALATION COMPOUNDS FROM STAGE 3 TO STAGE 2

The kinetics of the intercalation of graphite was investigated by means of X ray diffraction during the intercalation of potassium into highly oriented pyrolytic graphite. The results show that a long range order intermediate phase—stage (2 4) appears in the interconversion of stage 2 and stage 3. The structural unit of stage (2 4) is made up of two parts:one structural unit of stage 2 and one structural unit of stage 4. The length of structural unit of stage (2 4) is twice as much as that of stage 3. An ideal model of structural changes in stage 3→2 transition is suggested. The changes of orientation of carbon layers in stage 3 K GIC during the stage 3→2 transition are explained by using the model. The carbon layers stacking sequence of stage 2 K GIC inferred by the model is same as that determined by experiment.The carbon layers stacking sequence of stage (2 4) guessed by the model should be a|ab|bcbc|ca|abab|bc|caca.