  We study the topological configurations and dynamics of individual point
defect vacancies and interstitials in a two-dimensional colloidal crystal. Our
Brownian dynamics simulations show that the diffusion mechanism for vacancy
defects occurs in two phases. The defect can glide along the crystal lattice
directions, and it can rotate during an excited topological transition
configuration to assume a different direction for the next period of gliding.
The results for the vacancy defects are in good agreement with recent
experiments. For the interstitial point defects, which were not studied in the
experiments, we find several of the same modes of motion as in the vacancy
defect case along with two additional diffusion pathways. The interstitial
defects are more mobile than the vacancy defects due to the more
two-dimensional nature of the diffusion of the interstitial defects.
