Lattice-simulation investigations of the migration of lithium in intercalated graphite

We have repeated a simulation investigation [Phys. Rev. B 37, 4180 (1988)] of the migration of a ${\mathrm{Li}}^{+}$ ion in ${\mathrm{C}}_6$Li using an improved method which takes account of bond directionality. We have also extended the study to the second-stage compound ${\mathrm{C}}_{12}$Li. The respective migration energies calculated, 0.24 and 0.35 eV, are within the range of reported experimental values, and we find relative energy wells for the ${\mathrm{Li}}^{+}$ ions in a ${\mathrm{C}}_6$ ring between those of the initial and final configurations.