  We present the results of an Eulerian adaptive mesh refinement (AMR)
hydrodynamical and N-body simulation in a $\Lambda$CDM cosmology. The
simulation incorporates common cooling and heating processes for primordial
gas. A specific halo finder has been designed and applied in order to extract a
sample of galaxy clusters directly obtained from the simulation without
considering any resimulating scheme. We have studied the evolutionary history
of the cluster halos, and classified them into three categories depending on
the merger events they have undergone: major mergers, minor mergers, and
relaxed clusters. The main properties of each one of these classes and the
differences among them are discussed. The collisions among galaxy clusters are
produced naturally by the non-linear evolution in the simulated cosmological
volume, no controlled collisions have been considered. We pay special attention
to discuss the role of merger events as a source of feedback and reheating, and
their effects on the existence of cool cores in galaxy clusters, as well as in
the scaling relations.
