  Atomic diffusion is usually understood as a succession of random, independent
displacements of an adatom over the surface's potential energy landscape.
Nevertheless, an analysis of Molecular Dynamics simulations of self-diffusion
on Cu(111) demonstrates the existence of different types of correlations in the
atomic jumps at all temperatures. Thus, the atomic displacements cannot be
correctly described in terms of a random walk model. This fact has a profound
impact on the determination and interpretation of diffusion coefficients.
