Atomic size effects in continuum modeling - art. no. 020601

Continuum modeling of many physical systems typically assumes that the spat ial extent of an atom is small compared to the quantities of interest and c an therefore be neglected. We show that this is valid only asymptotically. For many applications of practical interest, the spatial extent of a discre te atom cannot be neglected. We have developed a model for the description of epitaxial growth based on the levelset method, and find that we can accu rately predict quantities such as the island densities, if we implement bou ndary conditions in a region with atomic width, rather than just on a line without any spatial extent. Only in the limit of very large islands and isl and spacings can this be neglected.