Stochastic model of staging in graphite intercalation compounds

A stochastic model is presented for staging transitions in graphite intercalation compounds. Three types of kinetic processes are introduced into the domain model of Daumas and Herold, and a one-dimensional Monte Carlo simulation is carried out within the framework of a single-column model to study the time evolution of the system for a variety of cases of staging transitions. Results of Monte Carlo simulations from stage 3 to stage 2 after a sudden change of chemical potential show that the staging transition depends sensitively on the final value of the chemical potential μ_ftemperature of the system, and the kinetic coefficients. When μ_f is taken in a certain range in the phase diagram, the time evolution of the structure factor demonstrates the coexistence and no significant broadening of peaks corresponding to the initial and final stage states. For other values of μ_f it is observed that the staging transitions proceed via disordered states and in some cases the final states are also disordered. Similar results are obtained for staging transitions from stage 4 to stage 3. Simulations are also made for staging transitions in which the start is from stage 4 and suddenly μchanges to a value in the stage-2 stable region. It is found that the system transforms either directly into a stage-2 state or into a metastable stage-3 state without showing evidence of further transition into a final stage-2 state, depending upon the values of μ_f and kinetic coefficients. A discussion is presented on the possibility of observing an intermediate metastable stage-3 state during the transition from stage 4 to stage 2.