Molecular dynamics simulations reveal a new picture for diffusion dynamics on the surface of amorphous silicon. The primary transport mechanism differs substantially from that observed on crystalline surfaces, in which small numbers of highly mobile adatoms or vacancies form and subsequently diffuse over substantial distances. Instead, diffusion takes place via large numbers of single atoms or dimers that move roughly one atomic diameter and are associated with highly strained rings having four atoms. (C) 2010 Published by Elsevier Ltd.