  Impact phenomena of nanoclusters subject to thermal fluctuations are
numerically investigated. From the molecular dynamics simulation for colliding
two identical clusters, it is found that the restitution coefficient for
head-on collisions has a peak at a colliding speed due to the competition
between the cohesive interaction and the repulsive interaction of colliding
clusters. Some aspects of the collisions can be understood by the theory by
Brilliantov {\it et al.} (Phys. Rev. E {\bf 76}, 051302 (2007)), but many new
aspects are found from the simulation. In particular, we find that there are
some anomalous rebounds in which the restitution coefficient is larger than
unity. The phase diagrams of rebound processes against impact speed and the
cohesive parameter can be understood by a simple phenomenology.
