Recent developments in thin film manufacturing have given rise to an interest in the growth of nanocrystalline films on one hand, and using cluster deposition to grow epitaxial films on the other. Both kinds of films can be grown using cluster deposition at soft landing conditions. But for both kinds of growth one has to know the maximum cluster size for which a cluster becomes fully epitaxial with the substrate. Using molecular dynamics computer simulations we determine this cluster size limit for landing on a smooth surface in the temperature range 0-750 K. Below the limit completely epitaxial growth is possible, and above it a nanocrystalline phase will form.